Installation of new version of Ubuntu interrupted, many application not running, error message for updates

Hello andrea pavesi -

A lot depends on how far the install progressed.
What have we to work with ?
Post back the results of terminal commands:
lsb_release -a
cat /etc/issue
cat -n /etc/apt/sources.list

From these we have an indication if the package manager can heal its self and complete the upgrade.

-we can try-

Hi Bashing-om
thanks for your help. These are the results of your suggested instructions

andrea@andrea-Lenovo-Z50-75:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04.1 LTS
Release: 20.04
Codename: focal
andrea@andrea-Lenovo-Z50-75:~$ cat/etc/issue
bash: cat/etc/issue: File o directory non esistente
andrea@andrea-Lenovo-Z50-75:~$ cat -n/etc/apt/sources.list
cat: opzione non valida -- "/"
Try 'cat --help' for more information.

So what?
Thanks for any help

andrea pavesi;

So far so good; but,
You miss typed the commands:
cat /etc/issue : there is a space between "cat" and "/etc" -
cat -n /etc/apt/sources.list : there is a space between "cat" and "-n" also a space between "-n" and "/etc"

Try again post these outputs. so we know we can target the fix for this install.

-a work in progress-

Hi Bashing-om,
thanks again for your help. Below the results

andrea@andrea-Lenovo-Z50-75:~$ lsb_release-a
Traceback (most recent call last):
  File "/usr/lib/command-not-found", line 28, in <module>
    from CommandNotFound import CommandNotFound
  File "/usr/lib/python3/dist-packages/CommandNotFound/CommandNotFound.py", line 19, in <module>
    from CommandNotFound.db.db import SqliteDatabase
  File "/usr/lib/python3/dist-packages/CommandNotFound/db/db.py", line 5, in <module>
    import apt_pkg
ModuleNotFoundError: No module named 'apt_pkg'
andrea@andrea-Lenovo-Z50-75:~$ cat/etc/issue
bash: cat/etc/issue: File o directory non esistente
andrea@andrea-Lenovo-Z50-75:~$ cat-n/etc/apt/sources.list
bash: cat-n/etc/apt/sources.list: File o directory non esistente
andrea@andrea-Lenovo-Z50-75:~$

You have to be more careful when typing commands. Apparently you missed to correctly add space characters between the different parts of the commands.

Please try again and copy/paste the output that you receive for the following commands:

uname -a
cat /etc/issue
cat -n /etc/apt/sources.list
sudo apt update
sudo dpkg --audit

Thank you Manfred,
as you can read above I was told to eliminate the spaces and that's what I did. But I did it again like you suggested and the output for the first two command was:

andrea@andrea-Lenovo-Z50-75:~$ uname -a
Linux andrea-Lenovo-Z50-75 4.15.0-129-generic #132-Ubuntu SMP Thu Dec 10 14:02:26 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
andrea@andrea-Lenovo-Z50-75:~$ cat /etc/issue
Ubuntu 20.04.1 LTS \n \l

andrea@andrea-Lenovo-Z50-75:~$ cat -n /etc/apt/sources.list
     1 # deb cdrom:[Ubuntu 14.04.2 LTS _Trusty Tahr_ - Release amd64 (20150218.1)]/ trusty main restricted
     2
     3 # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
     4 # newer versions of the distribution.
     5 deb http://it.archive.ubuntu.com/ubuntu/ focal main restricted
     6 deb-src http://it.archive.ubuntu.com/ubuntu/ focal main restricted
     7
     8 ## Major bug fix updates produced after the final release of the
     9 ## distribution.
    10 deb http://it.archive.ubuntu.com/ubuntu/ focal-updates main restricted
    11 deb-src http://it.archive.ubuntu.com/ubuntu/ focal-updates main restricted
    12
    13 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
    14 ## team. Also, please note that software in universe WILL NOT receive any
    15 ## review or updates from the Ubuntu security team.
    16 deb http://it.archive.ubuntu.com/ubuntu/ focal universe
    17 deb-src http://it.archive.ubuntu.com/ubuntu/ focal universe
    18 deb http://it.archive.ubuntu.com/ubuntu/ focal-updates universe
    19 deb-src http://it.archive.ubuntu.com/ubuntu/ focal-updates universe
    20
    21 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
    22 ## team, and may not be under a free licence. Please satisfy yourself as to
    23 ## your rights to use the software. Also, please note that software in
    24 ## multiverse WILL NOT receive any review or updates from the Ubuntu
    25 ## security team.
    26 deb http://it.archive.ubuntu.com/ubuntu/ focal multiverse
    27 deb-src http://it.archive.ubuntu.com/ubuntu/ focal multiverse
    28 deb http://it.archive.ubuntu.com/ubuntu/ focal-updates multiverse
    29 deb-src http://it.archive.ubuntu.com/ubuntu/ focal-updates multiverse
    30
    31 ## N.B. software from this repository may not have been tested as
    32 ## extensively as that contained in the main release, although it includes
    33 ## newer versions of some applications which may provide useful features.
    34 ## Also, please note that software in backports WILL NOT receive any review
    35 ## or updates from the Ubuntu security team.
    36
    37
    38 ## Uncomment the following two lines to add software from Canonical's
    39 ## 'partner' repository.
    40 ## This software is not part of Ubuntu, but is offered by Canonical and the
    41 ## respective vendors as a service to Ubuntu users.
    42 deb http://archive.canonical.com/ubuntu focal partner
    43 deb-src http://archive.canonical.com/ubuntu focal partner
    44
    45 deb http://it.archive.ubuntu.com/ubuntu/ focal-proposed restricted universe main multiverse
    46 deb http://it.archive.ubuntu.com/ubuntu/ focal-backports restricted universe main multiverse
    47 deb http://security.ubuntu.com/ubuntu/ focal-security restricted multiverse universe main

For the third and fourth command, I was requested to enter the password butit was impossibble to type it in, even after closing and reopening the terminal window.
A lot of gratitude for any help

New results:

sudo apt update
Trovato:1 http://it.archive.ubuntu.com/ubuntu focal InRelease
Scaricamento di:2 http://it.archive.ubuntu.com/ubuntu focal-updates InRelease [114 kB]
Scaricamento di:3 http://security.ubuntu.com/ubuntu focal-security InRelease [109 kB]
Scaricamento di:4 http://archive.canonical.com/ubuntu focal InRelease [12,1 kB]
Scaricamento di:5 http://it.archive.ubuntu.com/ubuntu focal-proposed InRelease [267 kB]
Scaricamento di:6 http://it.archive.ubuntu.com/ubuntu focal-backports InRelease [101 kB]
Scaricamento di:7 http://it.archive.ubuntu.com/ubuntu focal-updates/universe Sources [142 kB]
Scaricamento di:8 http://it.archive.ubuntu.com/ubuntu focal-updates/restricted Sources [8.092 B]
Scaricamento di:9 http://it.archive.ubuntu.com/ubuntu focal-updates/main Sources [351 kB]
Scaricamento di:10 http://it.archive.ubuntu.com/ubuntu focal-updates/multiverse Sources [8.712 B]
Scaricamento di:11 http://it.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages [731 kB]
Scaricamento di:12 http://archive.canonical.com/ubuntu focal/partner Sources [1.276 B]
Scaricamento di:13 http://archive.canonical.com/ubuntu focal/partner amd64 Packages [1.164 B]
Scaricamento di:14 http://archive.canonical.com/ubuntu focal/partner Translation-en [884 B]
Scaricamento di:15 http://it.archive.ubuntu.com/ubuntu focal-updates/main i386 Packages [400 kB]
Scaricamento di:16 http://it.archive.ubuntu.com/ubuntu focal-updates/main Translation-en [182 kB]
Scaricamento di:17 http://it.archive.ubuntu.com/ubuntu focal-updates/main amd64 DEP-11 Metadata [265 kB]
Scaricamento di:18 http://it.archive.ubuntu.com/ubuntu focal-updates/main amd64 c-n-f Metadata [11,5 kB]
Scaricamento di:19 http://it.archive.ubuntu.com/ubuntu focal-updates/restricted amd64 Packages [110 kB]
Scaricamento di:20 http://it.archive.ubuntu.com/ubuntu focal-updates/restricted i386 Packages [13,3 kB]
Scaricamento di:21 http://it.archive.ubuntu.com/ubuntu focal-updates/restricted Translation-en [16,5 kB]
Scaricamento di:22 http://it.archive.ubuntu.com/ubuntu focal-updates/universe i386 Packages [534 kB]
Scaricamento di:23 http://it.archive.ubuntu.com/ubuntu focal-updates/universe amd64 Packages [722 kB]
Scaricamento di:24 http://it.archive.ubuntu.com/ubuntu focal-updates/universe Translation-en [145 kB]
Scaricamento di:25 http://it.archive.ubuntu.com/ubuntu focal-updates/universe amd64 DEP-11 Metadata [281 kB]
Scaricamento di:26 http://security.ubuntu.com/ubuntu focal-security/restricted amd64 Packages [87,3 kB]
Scaricamento di:27 http://it.archive.ubuntu.com/ubuntu focal-updates/universe DEP-11 48x48 Icons [188 kB]
Scaricamento di:28 http://it.archive.ubuntu.com/ubuntu focal-updates/universe DEP-11 64x64 Icons [324 kB]
Scaricamento di:29 http://it.archive.ubuntu.com/ubuntu focal-updates/universe amd64 c-n-f Metadata [15,0 kB]
Scaricamento di:30 http://it.archive.ubuntu.com/ubuntu focal-updates/multiverse i386 Packages [5.860 B]
Scaricamento di:31 http://it.archive.ubuntu.com/ubuntu focal-updates/multiverse amd64 Packages [19,5 kB]
Scaricamento di:32 http://it.archive.ubuntu.com/ubuntu focal-updates/multiverse Translation-en [4.476 B]
Scaricamento di:33 http://it.archive.ubuntu.com/ubuntu focal-updates/multiverse amd64 DEP-11 Metadata [2.468 B]
Scaricamento di:34 http://it.archive.ubuntu.com/ubuntu focal-updates/multiverse amd64 c-n-f Metadata [548 B]
Scaricamento di:35 http://it.archive.ubuntu.com/ubuntu focal-proposed/restricted amd64 Packages [1.084 B]
Scaricamento di:36 http://security.ubuntu.com/ubuntu focal-security/restricted Translation-en [13,6 kB]
Scaricamento di:37 http://security.ubuntu.com/ubuntu focal-security/multiverse amd64 Packages [832 B]
Scaricamento di:38 http://security.ubuntu.com/ubuntu focal-security/multiverse Translation-en [288 B]
Scaricamento di:39 http://security.ubuntu.com/ubuntu focal-security/universe amd64 Packages [523 kB]
Scaricamento di:40 http://it.archive.ubuntu.com/ubuntu focal-proposed/restricted Translation-en [460 B]
Scaricamento di:41 http://it.archive.ubuntu.com/ubuntu focal-proposed/universe amd64 Packages [47,7 kB]
Scaricamento di:42 http://it.archive.ubuntu.com/ubuntu focal-proposed/universe i386 Packages [27,7 kB]
Scaricamento di:43 http://it.archive.ubuntu.com/ubuntu focal-proposed/universe Translation-en [21,7 kB]
Scaricamento di:44 http://it.archive.ubuntu.com/ubuntu focal-proposed/universe amd64 DEP-11 Metadata [114 kB]
Scaricamento di:45 http://it.archive.ubuntu.com/ubuntu focal-proposed/universe DEP-11 48x48 Icons [95,1 kB]
Scaricamento di:46 http://it.archive.ubuntu.com/ubuntu focal-proposed/universe DEP-11 64x64 Icons [159 kB]
Scaricamento di:47 http://it.archive.ubuntu.com/ubuntu focal-proposed/universe amd64 c-n-f Metadata [1.716 B]
Scaricamento di:48 http://it.archive.ubuntu.com/ubuntu focal-proposed/main amd64 Packages [66,4 kB]
Scaricamento di:49 http://it.archive.ubuntu.com/ubuntu focal-proposed/main i386 Packages [24,1 kB]
Scaricamento di:50 http://it.archive.ubuntu.com/ubuntu focal-proposed/main Translation-en [20,4 kB]
Scaricamento di:51 http://it.archive.ubuntu.com/ubuntu focal-proposed/main amd64 DEP-11 Metadata [10,3 kB]
Scaricamento di:52 http://it.archive.ubuntu.com/ubuntu focal-proposed/main DEP-11 64x64 Icons [13,6 kB]
Scaricamento di:53 http://it.archive.ubuntu.com/ubuntu focal-proposed/main amd64 c-n-f Metadata [1.504 B]
Scaricamento di:54 http://it.archive.ubuntu.com/ubuntu focal-proposed/multiverse amd64 Packages [760 B]
Scaricamento di:55 http://it.archive.ubuntu.com/ubuntu focal-proposed/multiverse i386 Packages [8.148 B]
Scaricamento di:56 http://security.ubuntu.com/ubuntu focal-security/universe i386 Packages [415 kB]
Scaricamento di:57 http://it.archive.ubuntu.com/ubuntu focal-proposed/multiverse Translation-en [3.492 B]
Scaricamento di:58 http://it.archive.ubuntu.com/ubuntu focal-proposed/multiverse amd64 c-n-f Metadata [188 B]
Scaricamento di:59 http://it.archive.ubuntu.com/ubuntu focal-backports/universe amd64 DEP-11 Metadata [1.768 B]
Scaricamento di:60 http://security.ubuntu.com/ubuntu focal-security/universe Translation-en [70,2 kB]
Scaricamento di:61 http://security.ubuntu.com/ubuntu focal-security/universe amd64 DEP-11 Metadata [56,5 kB]
Scaricamento di:62 http://security.ubuntu.com/ubuntu focal-security/universe amd64 c-n-f Metadata [9.376 B]
Scaricamento di:63 http://security.ubuntu.com/ubuntu focal-security/main i386 Packages [172 kB]
Scaricamento di:64 http://security.ubuntu.com/ubuntu focal-security/main amd64 Packages [419 kB]
Scaricamento di:65 http://security.ubuntu.com/ubuntu focal-security/main Translation-en [94,8 kB]
Scaricamento di:66 http://security.ubuntu.com/ubuntu focal-security/main amd64 DEP-11 Metadata [24,3 kB]
Scaricamento di:67 http://security.ubuntu.com/ubuntu focal-security/main amd64 c-n-f Metadata [5.616 B]
Recuperati 7.595 kB in 3s (2.354 kB/s)
Traceback (most recent call last):
  File "/usr/lib/cnf-update-db", line 8, in <module>
    from CommandNotFound.db.creator import DbCreator
  File "/usr/lib/python3/dist-packages/CommandNotFound/db/creator.py", line 11, in <module>
    import apt_pkg
ModuleNotFoundError: No module named 'apt_pkg'
Lettura elenco dei pacchetti... Fatto
E: Problem executing scripts APT::Update::Post-Invoke-Success 'if /usr/bin/test -w /var/lib/command-not-found/ -a -e /usr/lib/cnf-update-db; then /usr/lib/cnf-update-db > /dev/null; fi'
E: Sub-process returned an error code
andrea@andrea-Lenovo-Z50-75:~$

andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg --audit
I seguenti pacchetti sono stati estratti, ma non ancora configurati.
È necessario configurarli usando "dpkg --configure" o l'opzione di
configurazione nel menù di dselect affinché funzionino:
 backintime-qt simple backup/snapshot system (graphical interface)
 backintime-qt4 Qt 4 front-end for backintime (transitional package)
 calibre powerful and easy to use e-book manager
 calibre-bin powerful and easy to use e-book manager
 debconf-i18n full internationalization support for debconf
 libkf5auth5:amd64 Abstraction to system policy and authentication features
 libkf5authcore5:amd64 Abstraction to system policy and authentication features
 libkf5configwidgets5:amd64 Extra widgets for easier configuration support.
 libkf5xmlgui5:amd64 User configurable main windows.
 libpam-systemd:amd64 system and service manager - PAM module
 libpolkit-qt5-1-1:amd64 PolicyKit-qt5-1 library
 onboard Simple On-screen Keyboard
 onboard-data Language model files for the word suggestion feature of O
 python3-apsw another Python SQLite 3 wrapper (Python 3 version)
 python3-chm Python binding for CHMLIB - Python 3
 python3-dbus.mainloop.pyqt5 D-Bus Qt main loop support for Python 3
 python3-debconf interact with debconf from Python 3
 python3-html5-parser fast, standards compliant, C based, HTML 5 parser for pyt
 python3-msgpack Python 3 implementation of MessagePack format
 python3-pyqt5 Python 3 bindings for Qt5
 python3-pyqt5.qtsvg Python 3 bindings for Qt5's SVG module
 python3-pyqt5.qtwebchannel Python 3 bindings for Qt5's WebChannel module
 python3-pyqt5.qtwebengine Python 3 bindings for Qt5's WebEngine module
 python3-regex alternative regular expression module (Python 3)
 python3-renderpm:amd64 python low level render interface
 python3-sip Python 3/C++ bindings generator runtime library
 snapd Daemon and tooling that enable snap packages
 systemd system and service manager
 systemd-timesyncd minimalistic service to synchronize local time with NTP s

Thanks a lot for any help

I guess this was a misunderstanding. What Bashing-om wanted to tell is that there was already a space character missing, and not that you should leave them out.

Apparently you have found out that for a "sudo ..." command you have to "blind" type the password, because you do not get any feedback on screen (no echo, not even '*' placeholders).

And for your problem with the package management:
Execute the commands

sudo dpkg --configure -a
sudo apt install --reinstall python3-apt -f

and copy/paste the results that you receive, that we can check.

Output of your suggested commands:
andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg --configure -a
[sudo] password di andrea:
dpkg: problemi con le dipendenze impediscono la configurazione di python3-pyqt5.qtwebengine:
 python3-pyqt5.qtwebengine dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-pyqt5.qtwebengine (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di calibre:
 calibre dipende da python3-pyqt5.qtwebengine (>= 5.12.1-4+b1); tuttavia:
  Il pacchetto python3-pyqt5.qtwebengine non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto calibre (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di debconf-i18n:
 debconf-i18n dipende da debconf (= 1.5.73); tuttavia:
  La versione di debconf nel sistema è 1.5.66ubuntu1.

dpkg: errore nell'elaborare il pacchetto debconf-i18n (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-pyqt5:
 python3-pyqt5 dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-pyqt5 (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-html5-parser:
 python3-html5-parser dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-html5-parser (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-chm:
 python3-chm dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-chm (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-msgpack:
 python3-msgpack dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-msgpack (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-pyqt5.qtwebchannel:
 python3-pyqt5.qtwebchannel dipende da python3-pyqt5 (= 5.14.1+dfsg-3build1); tuttavia:
  Il pacchetto python3-pyqt5 non è ancora configurato.
 python3-pyqt5.qtwebchannel dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-pyqt5.qtwebchannel (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-pyqt5.qtsvg:
 python3-pyqt5.qtsvg dipende da python3-pyqt5 (= 5.14.1+dfsg-3build1); tuttavia:
  Il pacchetto python3-pyqt5 non è ancora configurato.
 python3-pyqt5.qtsvg dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-pyqt5.qtsvg (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-regex:
 python3-regex dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-regex (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-apsw:
 python3-apsw dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-apsw (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di backintime-qt:
 backintime-qt dipende da python3-pyqt5; tuttavia:
  Il pacchetto python3-pyqt5 non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto backintime-qt (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-debconf:
 python3-debconf dipende da debconf (= 1.5.73); tuttavia:
  La versione di debconf nel sistema è 1.5.66ubuntu1.

dpkg: errore nell'elaborare il pacchetto python3-debconf (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di systemd:
 systemd dipende da libsystemd0 (= 245.4-4ubuntu3.3); tuttavia:
  La versione di libsystemd0:amd64 nel sistema è 237-3ubuntu10.43.

dpkg: errore nell'elaborare il pacchetto systemd (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di backintime-qt4:
 backintime-qt4 dipende da backintime-qt; tuttavia:
  Il pacchetto backintime-qt non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto backintime-qt4 (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-sip:
 python3-sip dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-sip (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-dbus.mainloop.pyqt5:
 python3-dbus.mainloop.pyqt5 dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-dbus.mainloop.pyqt5 (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di onboard:
 onboard dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto onboard (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di python3-renderpm:amd64:
 python3-renderpm:amd64 dipende da python3 (>= 3.8~); tuttavia:
  La versione di python3 nel sistema è 3.6.7-1~18.04.

dpkg: errore nell'elaborare il pacchetto python3-renderpm:amd64 (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di systemd-timesyncd:
 systemd-timesyncd dipende da systemd (= 245.4-4ubuntu3.3); tuttavia:
  Il pacchetto systemd non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto systemd-timesyncd (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di libpam-systemd:amd64:
 libpam-systemd:amd64 dipende da systemd (= 245.4-4ubuntu3.3); tuttavia:
  Il pacchetto systemd non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto libpam-systemd:amd64 (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di libpolkit-qt5-1-1:amd64:
 libpolkit-qt5-1-1:amd64 dipende da default-logind | logind; tuttavia:
  Il pacchetto default-logind non è installato.
  Il pacchetto libpam-systemd:amd64 che fornisce default-logind non è ancora configurato.
  Il pacchetto logind non è installato.
  Il pacchetto systemd-services che fornisce logind non è installato.
  Il pacchetto libpam-systemd:amd64 che fornisce logind non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto libpolkit-qt5-1-1:amd64 (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di libkf5authcore5:amd64:
 libkf5authcore5:amd64 dipende da libpolkit-qt5-1-1 (>= 0.113.0); tuttavia:
  Il pacchetto libpolkit-qt5-1-1:amd64 non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto libkf5authcore5:amd64 (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di libkf5auth5:amd64:
 libkf5auth5:amd64 dipende da libkf5authcore5 (= 5.68.0-0ubuntu1); tuttavia:
  Il pacchetto libkf5authcore5:amd64 non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto libkf5auth5:amd64 (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di snapd:
 snapd dipende da systemd; tuttavia:
  Il pacchetto systemd non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto snapd (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di calibre-bin:
 calibre-bin dipende da sip-py3api-12.7; tuttavia:
  Il pacchetto sip-py3api-12.7 non è installato.
  Il pacchetto python3-sip che fornisce sip-py3api-12.7 non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto calibre-bin (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di onboard-data:
 onboard-data dipende da onboard (<< 1.4.1-2ubuntu7.1); tuttavia:
  Il pacchetto onboard non è ancora configurato.
 onboard-data dipende da onboard (>= 1.4.1-2ubuntu7); tuttavia:
  Il pacchetto onboard non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto onboard-data (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di libkf5configwidgets5:amd64:
 libkf5configwidgets5:amd64 dipende da libkf5authcore5 (>= 5.56.0); tuttavia:
  Il pacchetto libkf5authcore5:amd64 non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto libkf5configwidgets5:amd64 (--configure):
 problemi con le dipendenze - lasciato non configurato
dpkg: problemi con le dipendenze impediscono la configurazione di libkf5xmlgui5:amd64:
 libkf5xmlgui5:amd64 dipende da libkf5configwidgets5 (>= 5.67.0); tuttavia:
  Il pacchetto libkf5configwidgets5:amd64 non è ancora configurato.

dpkg: errore nell'elaborare il pacchetto libkf5xmlgui5:amd64 (--configure):
 problemi con le dipendenze - lasciato non configurato
Si sono verificati degli errori nell'elaborazione:
 python3-pyqt5.qtwebengine
 calibre
 debconf-i18n
 python3-pyqt5
 python3-html5-parser
 python3-chm
 python3-msgpack
 python3-pyqt5.qtwebchannel
 python3-pyqt5.qtsvg
 python3-regex
 python3-apsw
 backintime-qt
 python3-debconf
 systemd
 backintime-qt4
 python3-sip
 python3-dbus.mainloop.pyqt5
 onboard
 python3-renderpm:amd64
 systemd-timesyncd
 libpam-systemd:amd64
 libpolkit-qt5-1-1:amd64
 libkf5authcore5:amd64
 libkf5auth5:amd64
 snapd
 calibre-bin
 onboard-data
 libkf5configwidgets5:amd64
 libkf5xmlgui5:amd64
andrea@andrea-Lenovo-Z50-75:~$ sudo apt install --reinstall python3-apt -f
Lettura elenco dei pacchetti... Fatto
Generazione albero delle dipendenze
Lettura informazioni sullo stato... Fatto
È utile eseguire "apt --fix-broken install" per correggere ciò.
I seguenti pacchetti hanno dipendenze non soddisfatte:
 bleachbit : Dipende: python-gtk2 ma non è installabile
             Dipende: python:any (>= 2.7.5-5~)
             Raccomanda: python-notify ma non è installabile
 debconf-i18n : Dipende: debconf (= 1.5.73) ma la versione 1.5.66ubuntu1 sta per essere installata
 ibus-pinyin : Dipende: python:any (>= 2.7.5-5~)
 libnss-systemd : Dipende: systemd (= 237-3ubuntu10.43)
 libqt4-declarative : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-designer : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-help : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-network : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-script : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-scripttools : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-sql : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-sql-sqlite : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-svg : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-test : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-xml : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-xmlpatterns : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqtassistantclient4 : Dipende: libqtcore4 (>= 4:4.8.1) ma non è installabile
 libqtdbus4 : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqtgui4 : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 mercurial : Dipende: python (< 2.8)
             Dipende: python (>= 2.7~)
             Dipende: python:any (< 2.8)
             Dipende: python:any (>= 2.7~)
 mercurial-common : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 onboard : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python-apsw : Dipende: python (< 2.8)
               Dipende: python (>= 2.7~)
               Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7~)
 python-asn1crypto : Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-bs4 : Dipende: python:any (< 2.8)
              Dipende: python:any (>= 2.7.5-5~)
 python-cairo : Dipende: python (< 2.8)
                Dipende: python (>= 2.7~)
                Dipende: python:any (< 2.8)
                Dipende: python:any (>= 2.7.5-5~)
 python-cffi-backend : Dipende: python (< 2.8)
                       Dipende: python (>= 2.7~)
                       Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7~)
 python-chardet : Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-cherrypy3 : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-cryptography : Dipende: python (< 2.8)
                       Dipende: python (>= 2.7~)
                       Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7.5-5~)
 python-cssselect : Dipende: python
 python-cssutils : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-dateutil : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-dnspython : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-enum34 : Dipende: python:any (< 2.8)
                 Dipende: python:any (>= 2.7.5-5~)
 python-feedparser : Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-gi : Dipende: python (< 2.8)
             Dipende: python (>= 2.7~)
             Dipende: python:any (< 2.8)
             Dipende: python:any (>= 2.7.5-5~)
 python-gnucash : Dipende: python (< 2.8)
                  Dipende: python (>= 2.7~)
                  Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
                  Dipende: python-gtk2 ma non è installabile
 python-gobject-2 : Dipende: python (< 2.8)
                    Dipende: python (>= 2.7~)
                    Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-html5-parser : Dipende: python (< 2.8)
                       Dipende: python (>= 2.7~)
                       Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7.5-5~)
 python-html5lib : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-idna : Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7.5-5~)
 python-ipaddress : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-lxml : Dipende: python (< 2.8)
               Dipende: python (>= 2.7~)
               Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7.5-5~)
 python-markdown : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-mechanize : Dipende: python (>= 2.7.1-0ubuntu2)
                    Dipende: python (< 2.8)
 python-msgpack : Dipende: python (< 2.8)
                  Dipende: python (>= 2.7~)
                  Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-netifaces : Dipende: python (< 2.8)
                    Dipende: python (>= 2.7)
 python-olefile : Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-openssl : Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-pkg-resources : Dipende: python:any (< 2.8)
                        Dipende: python:any (>= 2.7.5-5~)
 python-pyparsing : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-regex : Dipende: python (< 2.8)
                Dipende: python (>= 2.7~)
                Dipende: python:any (< 2.8)
                Dipende: python:any (>= 2.7.5-5~)
 python-repoze.lru : Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-routes : Dipende: python:any (< 2.8)
                 Dipende: python:any (>= 2.7.5-5~)
 python-simplejson : Dipende: python (< 2.8)
                     Dipende: python (>= 2.7~)
                     Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-six : Dipende: python:any (< 2.8)
              Dipende: python:any (>= 2.7.5-5~)
 python-utidylib : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-webencodings : Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7.5-5~)
 python-webob : Dipende: python:any (< 2.8)
                Dipende: python:any (>= 2.7.5-5~)
 python-yaml : Dipende: python (< 2.8)
               Dipende: python (>= 2.7~)
               Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7.5-5~)
 python-zeitgeist : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python3 : Pre-dipende: python3-minimal (= 3.6.7-1~18.04) ma la versione 3.8.2-0ubuntu2 sta per essere installata
           Dipende: libpython3-stdlib (= 3.6.7-1~18.04) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-apsw : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-apt : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-chm : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-dbus.mainloop.pyqt5 : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-dbus.mainloop.qt : Dipende: libqtcore4 (>= 4:4.8.0-1~) ma non è installabile
 python3-debconf : Dipende: debconf (= 1.5.73) ma la versione 1.5.66ubuntu1 sta per essere installata
 python3-html5-parser : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-msgpack : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-pyqt4 : Dipende: libqtcore4 (>= 4:4.8.0-1~) ma non è installabile
 python3-pyqt5 : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-pyqt5.qtsvg : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-pyqt5.qtwebchannel : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-pyqt5.qtwebengine : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-regex : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-renderpm : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 python3-sip : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 sta per essere installata
 qdbus : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 qt-at-spi : Dipende: libqtcore4 (>= 4:4.8~) ma non è installabile
 sni-qt : Dipende: libqtcore4 (>= 4:4.7.3-1ubuntu3~) ma non è installabile
          Dipende: libdbusmenu-qt2 ma non è installabile
 systemd : Dipende: libsystemd0 (= 245.4-4ubuntu3.3) ma la versione 237-3ubuntu10.43 sta per essere installata
E: Dipendenze non soddisfatte. Provare "apt --fix-broken install" senza pacchetti (o specificare una soluzione).
andrea@andrea-Lenovo-Z50-75:~$

Most of the error messages seem to point towards a problem with the pytgon3 package.

What output do you receive for

sudo apt install python3 -f

Thanks Manfeed, this is the output:
andrea@andrea-Lenovo-Z50-75:~$ sudo apt install python3 -f
[sudo] password di andrea:
Lettura elenco dei pacchetti... Fatto
Generazione albero delle dipendenze
Lettura informazioni sullo stato... Fatto
È utile eseguire "apt --fix-broken install" per correggere ciò.
I seguenti pacchetti hanno dipendenze non soddisfatte:
 bleachbit : Dipende: python-gtk2 ma non è installabile
             Dipende: python:any (>= 2.7.5-5~)
             Raccomanda: python-notify ma non è installabile
 debconf-i18n : Dipende: debconf (= 1.5.73) ma la versione 1.5.66ubuntu1 sta per essere installata
 hplip : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 ibus-pinyin : Dipende: python:any (>= 2.7.5-5~)
 libnss-systemd : Dipende: systemd (= 237-3ubuntu10.43)
 libqt4-declarative : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-designer : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-help : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-network : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-script : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-scripttools : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-sql : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-sql-sqlite : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-svg : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-test : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-xml : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-xmlpatterns : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqtassistantclient4 : Dipende: libqtcore4 (>= 4:4.8.1) ma non è installabile
 libqtdbus4 : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqtgui4 : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 mercurial : Dipende: python (< 2.8)
             Dipende: python (>= 2.7~)
             Dipende: python:any (< 2.8)
             Dipende: python:any (>= 2.7~)
 mercurial-common : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-apsw : Dipende: python (< 2.8)
               Dipende: python (>= 2.7~)
               Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7~)
 python-asn1crypto : Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-bs4 : Dipende: python:any (< 2.8)
              Dipende: python:any (>= 2.7.5-5~)
 python-cairo : Dipende: python (< 2.8)
                Dipende: python (>= 2.7~)
                Dipende: python:any (< 2.8)
                Dipende: python:any (>= 2.7.5-5~)
 python-cffi-backend : Dipende: python (< 2.8)
                       Dipende: python (>= 2.7~)
                       Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7~)
 python-chardet : Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-cherrypy3 : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-cryptography : Dipende: python (< 2.8)
                       Dipende: python (>= 2.7~)
                       Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7.5-5~)
 python-cssselect : Dipende: python
 python-cssutils : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-dateutil : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-dnspython : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-enum34 : Dipende: python:any (< 2.8)
                 Dipende: python:any (>= 2.7.5-5~)
 python-feedparser : Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-gi : Dipende: python (< 2.8)
             Dipende: python (>= 2.7~)
             Dipende: python:any (< 2.8)
             Dipende: python:any (>= 2.7.5-5~)
 python-gnucash : Dipende: python (< 2.8)
                  Dipende: python (>= 2.7~)
                  Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
                  Dipende: python-gtk2 ma non è installabile
 python-gobject-2 : Dipende: python (< 2.8)
                    Dipende: python (>= 2.7~)
                    Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-html5-parser : Dipende: python (< 2.8)
                       Dipende: python (>= 2.7~)
                       Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7.5-5~)
 python-html5lib : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-idna : Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7.5-5~)
 python-ipaddress : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-lxml : Dipende: python (< 2.8)
               Dipende: python (>= 2.7~)
               Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7.5-5~)
 python-markdown : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-mechanize : Dipende: python (>= 2.7.1-0ubuntu2)
                    Dipende: python (< 2.8)
 python-msgpack : Dipende: python (< 2.8)
                  Dipende: python (>= 2.7~)
                  Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-netifaces : Dipende: python (< 2.8)
                    Dipende: python (>= 2.7)
 python-olefile : Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-openssl : Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-pkg-resources : Dipende: python:any (< 2.8)
                        Dipende: python:any (>= 2.7.5-5~)
 python-pyparsing : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-regex : Dipende: python (< 2.8)
                Dipende: python (>= 2.7~)
                Dipende: python:any (< 2.8)
                Dipende: python:any (>= 2.7.5-5~)
 python-repoze.lru : Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-routes : Dipende: python:any (< 2.8)
                 Dipende: python:any (>= 2.7.5-5~)
 python-simplejson : Dipende: python (< 2.8)
                     Dipende: python (>= 2.7~)
                     Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-six : Dipende: python:any (< 2.8)
              Dipende: python:any (>= 2.7.5-5~)
 python-utidylib : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-webencodings : Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7.5-5~)
 python-webob : Dipende: python:any (< 2.8)
                Dipende: python:any (>= 2.7.5-5~)
 python-yaml : Dipende: python (< 2.8)
               Dipende: python (>= 2.7~)
               Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7.5-5~)
 python-zeitgeist : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python3-apt : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-brlapi : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-cairo : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-cffi-backend : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-crypto : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-cups : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-dbus : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-dbus.mainloop.qt : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
                            Dipende: libqtcore4 (>= 4:4.8.0-1~) ma non è installabile
 python3-debconf : Dipende: debconf (= 1.5.73) ma la versione 1.5.66ubuntu1 sta per essere installata
 python3-gi : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-gi-cairo : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-lxml : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-markupsafe : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-nacl : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-netifaces : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-pil : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-protobuf : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-pyqt4 : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
                 Dipende: libqtcore4 (>= 4:4.8.0-1~) ma non è installabile
 python3-reportlab-accel : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-simplejson : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-systemd : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-uno : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-yaml : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 python3-zope.interface : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 qdbus : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 qt-at-spi : Dipende: libqtcore4 (>= 4:4.8~) ma non è installabile
 rhythmbox-plugins : Dipende: python3 (< 3.7) ma la versione 3.8.2-0ubuntu2 sta per essere installata
 sni-qt : Dipende: libqtcore4 (>= 4:4.7.3-1ubuntu3~) ma non è installabile
          Dipende: libdbusmenu-qt2 ma non è installabile
 systemd : Dipende: libsystemd0 (= 245.4-4ubuntu3.3) ma la versione 237-3ubuntu10.43 sta per essere installata
E: Dipendenze non soddisfatte. Provare "apt --fix-broken install" senza pacchetti (o specificare una soluzione).
andrea@andrea-Lenovo-Z50-75:~$

Ok. Apparently you have still some package installed in the version for Ubuntu 18.04 which now interfere with some other packages that are already in the version for Ubuntu 20.04.

What output do you receive for the command

sudo apt --fix-broken install

The output is:

andrea@andrea-Lenovo-Z50-75:~$ sudo apt --fix-broken install
[sudo] password di andrea:
Lettura elenco dei pacchetti... Fatto
Generazione albero delle dipendenze
Lettura informazioni sullo stato... Fatto
Correzione delle dipendenze... non riuscita.
I seguenti pacchetti hanno dipendenze non soddisfatte:
 bleachbit : Dipende: python-gtk2 ma non è installabile
             Dipende: python:any (>= 2.7.5-5~)
             Raccomanda: python-notify ma non è installabile
 debconf-i18n : Dipende: debconf (= 1.5.73) ma la versione 1.5.66ubuntu1 è installata
 ibus-pinyin : Dipende: python:any (>= 2.7.5-5~)
 libnss-systemd : Dipende: systemd (= 237-3ubuntu10.43)
 libqt4-declarative : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-designer : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-help : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-network : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-script : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-scripttools : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-sql : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-sql-sqlite : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-svg : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-test : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-xml : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqt4-xmlpatterns : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqtassistantclient4 : Dipende: libqtcore4 (>= 4:4.8.1) ma non è installabile
 libqtdbus4 : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 libqtgui4 : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 mercurial : Dipende: python (< 2.8)
             Dipende: python (>= 2.7~)
             Dipende: python:any (< 2.8)
             Dipende: python:any (>= 2.7~)
 mercurial-common : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 onboard : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python-apsw : Dipende: python (< 2.8)
               Dipende: python (>= 2.7~)
               Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7~)
 python-asn1crypto : Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-bs4 : Dipende: python:any (< 2.8)
              Dipende: python:any (>= 2.7.5-5~)
 python-cairo : Dipende: python (< 2.8)
                Dipende: python (>= 2.7~)
                Dipende: python:any (< 2.8)
                Dipende: python:any (>= 2.7.5-5~)
 python-cffi-backend : Dipende: python (< 2.8)
                       Dipende: python (>= 2.7~)
                       Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7~)
 python-chardet : Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-cherrypy3 : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-cryptography : Dipende: python (< 2.8)
                       Dipende: python (>= 2.7~)
                       Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7.5-5~)
 python-cssselect : Dipende: python
 python-cssutils : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-dateutil : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-dnspython : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-enum34 : Dipende: python:any (< 2.8)
                 Dipende: python:any (>= 2.7.5-5~)
 python-feedparser : Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-gi : Dipende: python (< 2.8)
             Dipende: python (>= 2.7~)
             Dipende: python:any (< 2.8)
             Dipende: python:any (>= 2.7.5-5~)
 python-gnucash : Dipende: python (< 2.8)
                  Dipende: python (>= 2.7~)
                  Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
                  Dipende: python-gtk2 ma non è installabile
 python-gobject-2 : Dipende: python (< 2.8)
                    Dipende: python (>= 2.7~)
                    Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-html5-parser : Dipende: python (< 2.8)
                       Dipende: python (>= 2.7~)
                       Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7.5-5~)
 python-html5lib : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-idna : Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7.5-5~)
 python-ipaddress : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-lxml : Dipende: python (< 2.8)
               Dipende: python (>= 2.7~)
               Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7.5-5~)
 python-markdown : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-mechanize : Dipende: python (>= 2.7.1-0ubuntu2)
                    Dipende: python (< 2.8)
 python-msgpack : Dipende: python (< 2.8)
                  Dipende: python (>= 2.7~)
                  Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-netifaces : Dipende: python (< 2.8)
                    Dipende: python (>= 2.7)
 python-olefile : Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-openssl : Dipende: python:any (< 2.8)
                  Dipende: python:any (>= 2.7.5-5~)
 python-pkg-resources : Dipende: python:any (< 2.8)
                        Dipende: python:any (>= 2.7.5-5~)
 python-pyparsing : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python-regex : Dipende: python (< 2.8)
                Dipende: python (>= 2.7~)
                Dipende: python:any (< 2.8)
                Dipende: python:any (>= 2.7.5-5~)
 python-repoze.lru : Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-routes : Dipende: python:any (< 2.8)
                 Dipende: python:any (>= 2.7.5-5~)
 python-simplejson : Dipende: python (< 2.8)
                     Dipende: python (>= 2.7~)
                     Dipende: python:any (< 2.8)
                     Dipende: python:any (>= 2.7.5-5~)
 python-six : Dipende: python:any (< 2.8)
              Dipende: python:any (>= 2.7.5-5~)
 python-utidylib : Dipende: python:any (< 2.8)
                   Dipende: python:any (>= 2.7.5-5~)
 python-webencodings : Dipende: python:any (< 2.8)
                       Dipende: python:any (>= 2.7.5-5~)
 python-webob : Dipende: python:any (< 2.8)
                Dipende: python:any (>= 2.7.5-5~)
 python-yaml : Dipende: python (< 2.8)
               Dipende: python (>= 2.7~)
               Dipende: python:any (< 2.8)
               Dipende: python:any (>= 2.7.5-5~)
 python-zeitgeist : Dipende: python:any (< 2.8)
                    Dipende: python:any (>= 2.7.5-5~)
 python3 : Pre-dipende: python3-minimal (= 3.6.7-1~18.04) ma la versione 3.8.2-0ubuntu2 è installata
           Dipende: libpython3-stdlib (= 3.6.7-1~18.04) ma la versione 3.8.2-0ubuntu2 è installata
 python3-apsw : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-chm : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-dbus.mainloop.pyqt5 : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-dbus.mainloop.qt : Dipende: libqtcore4 (>= 4:4.8.0-1~) ma non è installabile
 python3-debconf : Dipende: debconf (= 1.5.73) ma la versione 1.5.66ubuntu1 è installata
 python3-html5-parser : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-msgpack : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-pyqt4 : Dipende: libqtcore4 (>= 4:4.8.0-1~) ma non è installabile
 python3-pyqt5 : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-pyqt5.qtsvg : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-pyqt5.qtwebchannel : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-pyqt5.qtwebengine : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-regex : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-renderpm : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 python3-sip : Dipende: python3 (>= 3.8~) ma la versione 3.6.7-1~18.04 è installata
 qdbus : Dipende: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) ma non è installabile
 qt-at-spi : Dipende: libqtcore4 (>= 4:4.8~) ma non è installabile
 sni-qt : Dipende: libqtcore4 (>= 4:4.7.3-1ubuntu3~) ma non è installabile
          Dipende: libdbusmenu-qt2 ma non è installabile
 systemd : Dipende: libsystemd0 (= 245.4-4ubuntu3.3) ma la versione 237-3ubuntu10.43 è installata
E: Errore, pkgProblemResolver::Resolve ha generato delle interruzioni. Questo potrebbe essere causato da pacchetti bloccati.
E: Impossibile correggere le dipendenze
andrea@andrea-Lenovo-Z50-75:~$

It seems that this is going to be complicated.

What is the output of the command

apt-cache policy python python3 libqt4-declarative libqtcore4

andrea@andrea-Lenovo-Z50-75:~$ apt-cache policy python python3 libqt4-declarative libqtcore4
python:
  Installato: (nessuno)
  Candidato: (nessuno)
  Tabella versione:
     2.7.15~rc1-1 -1
        100 /var/lib/dpkg/status
python3:
  Installato: 3.6.7-1~18.04
  Candidato: 3.8.2-0ubuntu2
  Tabella versione:
     3.8.2-0ubuntu2 500
        500 http://it.archive.ubuntu.com/ubuntu focal/main amd64 Packages
 *** 3.6.7-1~18.04 100
        100 /var/lib/dpkg/status
libqt4-declarative:
  Installato: 4:4.8.7+dfsg-7ubuntu1
  Candidato: 4:4.8.7+dfsg-7ubuntu1
  Tabella versione:
 *** 4:4.8.7+dfsg-7ubuntu1 100
        100 /var/lib/dpkg/status
libqtcore4:
  Installato: (nessuno)
  Candidato: (nessuno)
  Tabella versione:
     4:4.8.7+dfsg-7ubuntu1 -1
        100 /var/lib/dpkg/status
andrea@andrea-Lenovo-Z50-75:~$

An attempt to repair the packages depending on Python 2 as a first step:

Issue the commands

wget https://launchpad.net/ubuntu/+archive/primary/+files/python_2.7.15~rc1-1_amd64.deb
sudo dpkg -i python_2.7.15~rc1-1_amd64.deb

and copy/paste the output that we can check.

andrea@andrea-Lenovo-Z50-75:~$ wget https://launchpad.net/ubuntu/+archive/primary/+files/python_2.7.15~rc1-1_amd64.deb
--2021-01-07 22:42:48-- https://launchpad.net/ubuntu/+archive/primary/+files/python_2.7.15~rc1-1_amd64.deb
Risoluzione di launchpad.net (launchpad.net)... 91.189.89.222, 91.189.89.223, 2001:67c:1560:8003::8004, ...
Connessione a launchpad.net (launchpad.net)|91.189.89.222|:443... connesso.
Richiesta HTTP inviata, in attesa di risposta... 303 See Other
Posizione: https://launchpadlibrarian.net/365782557/python_2.7.15~rc1-1_amd64.deb [segue]
--2021-01-07 22:42:48-- https://launchpadlibrarian.net/365782557/python_2.7.15~rc1-1_amd64.deb
Risoluzione di launchpadlibrarian.net (launchpadlibrarian.net)... 91.189.89.228, 91.189.89.229, 2001:67c:1560:8003::8008, ...
Connessione a launchpadlibrarian.net (launchpadlibrarian.net)|91.189.89.228|:443... connesso.
Richiesta HTTP inviata, in attesa di risposta... 200 OK
Lunghezza: 139968 (137K) [application/x-debian-package]
Salvataggio in: "python_2.7.15~rc1-1_amd64.deb"

python_2.7.15~rc1 100%[============>] 136,69K --.-KB/s in 0,1s

2021-01-07 22:42:48 (1,23 MB/s) - "python_2.7.15~rc1-1_amd64.deb" salvato [139968/139968]

andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg -i python_2.7.15~rc1-1_amd64.deb
[sudo] password di andrea:
Selezionato il pacchetto python non precedentemente selezionato.
dpkg: problemi con le pre-dipendenze di python_2.7.15~rc1-1_amd64.deb contenente python:
 python pre-dipende da python-minimal (= 2.7.15~rc1-1)
  python-minimal non è installato.

dpkg: errore nell'elaborare l'archivio python_2.7.15~rc1-1_amd64.deb (--install):
 problema con le pre-dipendenze - python non viene installato
Si sono verificati degli errori nell'elaborazione:
 python_2.7.15~rc1-1_amd64.deb
andrea@andrea-Lenovo-Z50-75:~$

ok, try

wget https://launchpad.net/ubuntu/+archive/primary/+files/python-minimal_2.7.15~rc1-1_amd64.deb
sudo dpkg -i python-minimal_2.7.15~rc1-1_amd64.deb
wget https://launchpad.net/ubuntu/+archive/primary/+files/python_2.7.15~rc1-1_amd64.deb
sudo dpkg -i python_2.7.15~rc1-1_amd64.deb

and copy/paste the output as done before.

The output:
andrea@andrea-Lenovo-Z50-75:~$ wget https://launchpad.net/ubuntu/+archive/primary/+files/python-minimal_2.7.15~rc1-1_amd64.deb
--2021-01-07 22:49:23-- https://launchpad.net/ubuntu/+archive/primary/+files/python-minimal_2.7.15~rc1-1_amd64.deb
Risoluzione di launchpad.net (launchpad.net)... 91.189.89.223, 91.189.89.222, 2001:67c:1560:8003::8004, ...
Connessione a launchpad.net (launchpad.net)|91.189.89.223|:443... connesso.
Richiesta HTTP inviata, in attesa di risposta... 303 See Other
Posizione: https://launchpadlibrarian.net/365782556/python-minimal_2.7.15~rc1-1_amd64.deb [segue]
--2021-01-07 22:49:23-- https://launchpadlibrarian.net/365782556/python-minimal_2.7.15~rc1-1_amd64.deb
Risoluzione di launchpadlibrarian.net (launchpadlibrarian.net)... 91.189.89.228, 91.189.89.229, 2001:67c:1560:8003::8008, ...
Connessione a launchpadlibrarian.net (launchpadlibrarian.net)|91.189.89.228|:443... connesso.
Richiesta HTTP inviata, in attesa di risposta... 200 OK
Lunghezza: 28068 (27K) [application/x-debian-package]
Salvataggio in: "python-minimal_2.7.15~rc1-1_amd64.deb"

python-minimal_2.7. 100%[===================>] 27,41K --.-KB/s in 0,05s

2021-01-07 22:49:24 (563 KB/s) - "python-minimal_2.7.15~rc1-1_amd64.deb" salvato [28068/28068]

andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg -i python-minimal_2.7.15~rc1-1_amd64.deb
[sudo] password di andrea:
Selezionato il pacchetto python-minimal non precedentemente selezionato.
(Lettura del database... 360170 file e directory attualmente installati.)
Preparativi per estrarre python-minimal_2.7.15~rc1-1_amd64.deb...
Estrazione di python-minimal (2.7.15~rc1-1)...
Sostituiti dai file nel pacchetto python2-minimal (2.7.17-2ubuntu4) installato...
dpkg: problemi con le dipendenze impediscono la configurazione di python-minimal:
 python2-minimal (2.7.17-2ubuntu4) danneggia python-minimal (<< 2.7.15-2) ed è installato.
  La versione di python-minimal da configurare è 2.7.15~rc1-1.

dpkg: errore nell'elaborare il pacchetto python-minimal (--install):
 problemi con le dipendenze - lasciato non configurato
Elaborazione dei trigger per man-db (2.8.3-2ubuntu0.1)...
Si sono verificati degli errori nell'elaborazione:
 python-minimal
andrea@andrea-Lenovo-Z50-75:~$ wget https://launchpad.net/ubuntu/+archive/primary/+files/python_2.7.15~rc1-1_amd64.deb
--2021-01-07 22:50:38-- https://launchpad.net/ubuntu/+archive/primary/+files/python_2.7.15~rc1-1_amd64.deb
Risoluzione di launchpad.net (launchpad.net)... 91.189.89.223, 91.189.89.222, 2001:67c:1560:8003::8004, ...
Connessione a launchpad.net (launchpad.net)|91.189.89.223|:443... connesso.
Richiesta HTTP inviata, in attesa di risposta... 303 See Other
Posizione: https://launchpadlibrarian.net/365782557/python_2.7.15~rc1-1_amd64.deb [segue]
--2021-01-07 22:50:38-- https://launchpadlibrarian.net/365782557/python_2.7.15~rc1-1_amd64.deb
Risoluzione di launchpadlibrarian.net (launchpadlibrarian.net)... 91.189.89.229, 91.189.89.228, 2001:67c:1560:8003::8008, ...
Connessione a launchpadlibrarian.net (launchpadlibrarian.net)|91.189.89.229|:443... connesso.
Richiesta HTTP inviata, in attesa di risposta... 200 OK
Lunghezza: 139968 (137K) [application/x-debian-package]
Salvataggio in: "python_2.7.15~rc1-1_amd64.deb.1"

python_2.7.15~rc1-1 100%[===================>] 136,69K --.-KB/s in 0,1s

2021-01-07 22:50:39 (1,21 MB/s) - "python_2.7.15~rc1-1_amd64.deb.1" salvato [139968/139968]

andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg -i python_2.7.15~rc1-1_amd64.deb
dpkg: problemi con le pre-dipendenze di python_2.7.15~rc1-1_amd64.deb contenente python:
 python pre-dipende da python-minimal (= 2.7.15~rc1-1)
  python-minimal è stato estratto, ma non è mai stato configurato.

dpkg: errore nell'elaborare l'archivio python_2.7.15~rc1-1_amd64.deb (--install):
 problema con le pre-dipendenze - python non viene installato
Si sono verificati degli errori nell'elaborazione:
 python_2.7.15~rc1-1_amd64.deb
andrea@andrea-Lenovo-Z50-75:~$

ok, try

sudo dpkg --purge python2-minimal --force-depends
sudo dpkg -i python-minimal_2.7.15~rc1-1_amd64.deb
sudo dpkg -i python_2.7.15~rc1-1_amd64.deb

andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg --purge python2-minimal --force-depends
[sudo] password di andrea:
dpkg: errore: --purge richiede un nome di pacchetto valido. "--force-depends" non lo è: nome di pacchetto non valido nello specificatore "--force-depends": deve iniziare con un carattere alfanumerico

Usare dpkg --help per un aiuto sull'installazione e la rimozione dei pacchetti [*].
Usare "apt" o "aptitude" per un'interfaccia alla gestione dei pacchetti.
Usare dpkg -Dhelp per l'elenco delle opzioni di debug per dpkg.
Usare dpkg --force-help per l'elenco delle opzioni di forzatura.
Usare dpkg-deb --help per un aiuto sulla manipolazione dei file *.deb.

Le opzioni indicate con [*] producono output prolisso - creare una pipe con "less" o "more".
andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg -i python-minimal_2.7.15~rc1-1_amd64.deb
(Lettura del database... 360176 file e directory attualmente installati.)
Preparativi per estrarre python-minimal_2.7.15~rc1-1_amd64.deb...
Estrazione di python-minimal (2.7.15~rc1-1) su (2.7.15~rc1-1)...
Sostituiti dai file nel pacchetto python2-minimal (2.7.17-2ubuntu4) installato...
dpkg: problemi con le dipendenze impediscono la configurazione di python-minimal:
 python2-minimal (2.7.17-2ubuntu4) danneggia python-minimal (<< 2.7.15-2) ed è installato.
  La versione di python-minimal da configurare è 2.7.15~rc1-1.

dpkg: errore nell'elaborare il pacchetto python-minimal (--install):
 problemi con le dipendenze - lasciato non configurato
Elaborazione dei trigger per man-db (2.8.3-2ubuntu0.1)...
Si sono verificati degli errori nell'elaborazione:
 python-minimal
andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg -i python_2.7.15~rc1-1_amd64.deb
dpkg: problemi con le pre-dipendenze di python_2.7.15~rc1-1_amd64.deb contenente python:
 python pre-dipende da python-minimal (= 2.7.15~rc1-1)
  python-minimal è stato estratto, ma non è mai stato configurato.

dpkg: errore nell'elaborare l'archivio python_2.7.15~rc1-1_amd64.deb (--install):
 problema con le pre-dipendenze - python non viene installato
Si sono verificati degli errori nell'elaborazione:
 python_2.7.15~rc1-1_amd64.deb
andrea@andrea-Lenovo-Z50-75:~$

Sorry, my fault, wrong sequence, try again with

sudo dpkg --force-depends --purge python2-minimal
sudo dpkg -i python-minimal_2.7.15~rc1-1_amd64.deb
sudo dpkg -i python_2.7.15~rc1-1_amd64.deb

Here's the output:
andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg --force-depends --purge python2-minimal
[sudo] password di andrea:
dpkg: python2-minimal: problemi con le dipendenze, ma viene rimosso comunque:
 python2 dipende da python2-minimal (= 2.7.17-2ubuntu4).

(Lettura del database... 360175 file e directory attualmente installati.)
Rimozione di python2-minimal (2.7.17-2ubuntu4)...
Elaborazione dei trigger per man-db (2.8.3-2ubuntu0.1)...
andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg -i python-minimal_2.7.15~rc1-1_amd64.deb
(Lettura del database... 360153 file e directory attualmente installati.)
Preparativi per estrarre python-minimal_2.7.15~rc1-1_amd64.deb...
Estrazione di python-minimal (2.7.15~rc1-1) su (2.7.15~rc1-1)...
Configurazione di python-minimal (2.7.15~rc1-1)...
Elaborazione dei trigger per man-db (2.8.3-2ubuntu0.1)...
andrea@andrea-Lenovo-Z50-75:~$ sudo dpkg -i python_2.7.15~rc1-1_amd64.deb
(Lettura del database... 360172 file e directory attualmente installati.)
Preparativi per estrarre python_2.7.15~rc1-1_amd64.deb...
Estrazione di python (2.7.15~rc1-1)...
Sostituiti dai file nel pacchetto python2 (2.7.17-2ubuntu4) installato...
dpkg: problemi con le dipendenze impediscono la configurazione di python:
 python dipende da libpython-stdlib (= 2.7.15~rc1-1); tuttavia:
  Il pacchetto libpython-stdlib non è installato.
 python2 (2.7.17-2ubuntu4) danneggia python (<< 2.7.15-2) ed è installato.
  La versione di python da configurare è 2.7.15~rc1-1.

dpkg: errore nell'elaborare il pacchetto python (--install):
 problemi con le dipendenze - lasciato non configurato
Elaborazione dei trigger per doc-base (0.10.8)...
Elaborazione 1 file doc-base aggiunto...
Elaborazione dei trigger per man-db (2.8.3-2ubuntu0.1)...
Si sono verificati degli errori nell'elaborazione:
 python
andrea@andrea-Lenovo-Z50-75:~$

ok, a first very small step worked.
Continue with

wget https://launchpad.net/ubuntu/+archive/primary/+files/libpython-stdlib_2.7.15~rc1-1_amd64.deb
LANG=C sudo dpkg --force-depends --purge python2
LANG=C sudo dpkg -i libpython-stdlib_2.7.15~rc1-1_amd64.deb
LANG=C sudo dpkg -i python_2.7.15~rc1-1_amd64.deb

Glad opr the progress!
Next output:
andrea@andrea-Lenovo-Z50-75:~$ wget https://launchpad.net/ubuntu/+archive/primary/+files/libpython-stdlib_2.7.15~rc1-1_amd64.deb
--2021-01-07 23:15:43-- https://launchpad.net/ubuntu/+archive/primary/+files/libpython-stdlib_2.7.15~rc1-1_amd64.deb
Risoluzione di launchpad.net (launchpad.net)... 91.189.89.222, 91.189.89.223, 2001:67c:1560:8003::8003, ...
Connessione a launchpad.net (launchpad.net)|91.189.89.222|:443... connesso.
Richiesta HTTP inviata, in attesa di risposta... 303 See Other
Posizione: https://launchpadlibrarian.net/365782539/libpython-stdlib_2.7.15~rc1-1_amd64.deb [segue]
--2021-01-07 23:15:44-- https://launchpadlibrarian.net/365782539/libpython-stdlib_2.7.15~rc1-1_amd64.deb
Risoluzione di launchpadlibrarian.net (launchpadlibrarian.net)... 91.189.89.229, 91.189.89.228, 2001:67c:1560:8003::8007, ...
Connessione a launchpadlibrarian.net (launchpadlibrarian.net)|91.189.89.229|:443... connesso.
Richiesta HTTP inviata, in attesa di risposta... 200 OK
Lunghezza: 7620 (7,4K) [application/x-debian-package]
Salvataggio in: "libpython-stdlib_2.7.15~rc1-1_amd64.deb"

libpython-stdlib_2. 100%[===================>] 7,44K --.-KB/s in 0,001s

2021-01-07 23:15:44 (5,04 MB/s) - "libpython-stdlib_2.7.15~rc1-1_amd64.deb" salvato [7620/7620]

andrea@andrea-Lenovo-Z50-75:~$ LANG=C sudo dpkg --force-depends --purge python2
[sudo] password for andrea:
Sorry, try again.
[sudo] password for andrea:
dpkg: python2: dependency problems, but removing anyway as you requested:
 python-sip depends on python2 (<< 2.8).
 python-sip depends on python2 (>= 2.7~).
 python-sip depends on python2:any (<< 2.8).
 python-sip depends on python2:any (>= 2.7~).
 python-sip depends on python2 (<< 2.8).
 python-sip depends on python2 (>= 2.7~).
 python-sip depends on python2:any (<< 2.8).
 python-sip depends on python2:any (>= 2.7~).
 python-sip depends on python2 (<< 2.8).
 python-sip depends on python2 (>= 2.7~).
 python-sip depends on python2:any (<< 2.8).
 python-sip depends on python2:any (>= 2.7~).
 python-sip depends on python2 (<< 2.8).
 python-sip depends on python2 (>= 2.7~).
 python-sip depends on python2:any (<< 2.8).
 python-sip depends on python2:any (>= 2.7~).
 python-xdg depends on python2:any (<< 2.8).
 python-xdg depends on python2:any (>= 2.7~).
 python-xdg depends on python2:any (<< 2.8).
 python-xdg depends on python2:any (>= 2.7~).
 python-pil:amd64 depends on python2 (<< 2.8).
 python-pil:amd64 depends on python2 (>= 2.7~).
 python-pil:amd64 depends on python2:any (<< 2.8).
 python-pil:amd64 depends on python2:any (>= 2.7~).
 python-pil:amd64 depends on python2 (<< 2.8).
 python-pil:amd64 depends on python2 (>= 2.7~).
 python-pil:amd64 depends on python2:any (<< 2.8).
 python-pil:amd64 depends on python2:any (>= 2.7~).
 python-pil:amd64 depends on python2 (<< 2.8).
 python-pil:amd64 depends on python2 (>= 2.7~).
 python-pil:amd64 depends on python2:any (<< 2.8).
 python-pil:amd64 depends on python2:any (>= 2.7~).
 python-pil:amd64 depends on python2 (<< 2.8).
 python-pil:amd64 depends on python2 (>= 2.7~).
 python-pil:amd64 depends on python2:any (<< 2.8).
 python-pil:amd64 depends on python2:any (>= 2.7~).
 python-dbus depends on python2 (<< 2.8).
 python-dbus depends on python2 (>= 2.7~).
 python-dbus depends on python2:any (<< 2.8).
 python-dbus depends on python2:any (>= 2.7~).
 python-dbus depends on python2 (<< 2.8).
 python-dbus depends on python2 (>= 2.7~).
 python-dbus depends on python2:any (<< 2.8).
 python-dbus depends on python2:any (>= 2.7~).
 python-dbus depends on python2 (<< 2.8).
 python-dbus depends on python2 (>= 2.7~).
 python-dbus depends on python2:any (<< 2.8).
 python-dbus depends on python2:any (>= 2.7~).
 python-dbus depends on python2 (<< 2.8).
 python-dbus depends on python2 (>= 2.7~).
 python-dbus depends on python2:any (<< 2.8).
 python-dbus depends on python2:any (>= 2.7~).
 python-libxml2 depends on python2 (<< 2.8).
 python-libxml2 depends on python2 (>= 2.7~).
 python-libxml2 depends on python2:any (<< 2.8).
 python-libxml2 depends on python2:any (>= 2.7~).
 python-libxml2 depends on python2 (<< 2.8).
 python-libxml2 depends on python2 (>= 2.7~).
 python-libxml2 depends on python2:any (<< 2.8).
 python-libxml2 depends on python2:any (>= 2.7~).
 python-libxml2 depends on python2 (<< 2.8).
 python-libxml2 depends on python2 (>= 2.7~).
 python-libxml2 depends on python2:any (<< 2.8).
 python-libxml2 depends on python2:any (>= 2.7~).
 python-libxml2 depends on python2 (<< 2.8).
 python-libxml2 depends on python2 (>= 2.7~).
 python-libxml2 depends on python2:any (<< 2.8).
 python-libxml2 depends on python2:any (>= 2.7~).
 python-pygments depends on python2:any (<< 2.8).
 python-pygments depends on python2:any (>= 2.7~).
 python-pygments depends on python2:any (<< 2.8).
 python-pygments depends on python2:any (>= 2.7~).

(Reading database ... 360211 files and directories currently installed.)
Removing python2 (2.7.17-2ubuntu4) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
andrea@andrea-Lenovo-Z50-75:~$ LANG=C sudo dpkg -i libpython-stdlib_2.7.15~rc1-1_amd64.deb
Selecting previously unselected package libpython-stdlib:amd64.
(Reading database ... 360187 files and directories currently installed.)
Preparing to unpack libpython-stdlib_2.7.15~rc1-1_amd64.deb ...
Unpacking libpython-stdlib:amd64 (2.7.15~rc1-1) ...
dpkg: dependency problems prevent configuration of libpython-stdlib:amd64:
 libpython2-stdlib:amd64 (2.7.17-2ubuntu4) breaks libpython-stdlib (<< 2.7.15-2) and is installed.
  Version of libpython-stdlib:amd64 to be configured is 2.7.15~rc1-1.

dpkg: error processing package libpython-stdlib:amd64 (--install):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 libpython-stdlib:amd64
andrea@andrea-Lenovo-Z50-75:~$ LANG=C sudo dpkg -i python_2.7.15~rc1-1_amd64.deb
(Reading database ... 360191 files and directories currently installed.)
Preparing to unpack python_2.7.15~rc1-1_amd64.deb ...
Unpacking python (2.7.15~rc1-1) over (2.7.15~rc1-1) ...
dpkg: dependency problems prevent configuration of python:
 python depends on libpython-stdlib (= 2.7.15~rc1-1); however:
  Package libpython-stdlib:amd64 is not configured yet.

dpkg: error processing package python (--install):
 dependency problems - leaving unconfigured
Processing triggers for doc-base (0.10.8) ...
Processing 1 changed doc-base file...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Errors were encountered while processing:
 python
andrea@andrea-Lenovo-Z50-75:~$

ok, this needs another removal:

LANG=C sudo dpkg --force-depends --purge libpython2-stdlib
LANG=C sudo dpkg -i libpython-stdlib_2.7.15~rc1-1_amd64.deb
LANG=C sudo dpkg -i python_2.7.15~rc1-1_amd64.deb

andrea@andrea-Lenovo-Z50-75:~$ LANG=C sudo dpkg --force-depends --purge libpython2-stdlib
[sudo] password for andrea:
(Reading database ... 360201 files and directories currently installed.)
Removing libpython2-stdlib:amd64 (2.7.17-2ubuntu4) ...
andrea@andrea-Lenovo-Z50-75:~$ LANG=C sudo dpkg -i libpython-stdlib_2.7.15~rc1-1_amd64.deb
(Reading database ... 360198 files and directories currently installed.)
Preparing to unpack libpython-stdlib_2.7.15~rc1-1_amd64.deb ...
Unpacking libpython-stdlib:amd64 (2.7.15~rc1-1) over (2.7.15~rc1-1) ...
Setting up libpython-stdlib:amd64 (2.7.15~rc1-1) ...
andrea@andrea-Lenovo-Z50-75:~$ LANG=C sudo dpkg -i python_2.7.15~rc1-1_amd64.deb
(Reading database ... 360198 files and directories currently installed.)
Preparing to unpack python_2.7.15~rc1-1_amd64.deb ...
Unpacking python (2.7.15~rc1-1) over (2.7.15~rc1-1) ...
Setting up python (2.7.15~rc1-1) ...
Processing triggers for doc-base (0.10.8) ...
Processing 1 changed doc-base file...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
andrea@andrea-Lenovo-Z50-75:~$

ok, let's check whether the situation has improved compared to the beginning, what is now the output of the commands

LANG=C sudo dpkg --configure -a
LANG=C sudo apt --fix-broken install

(I have to stop now and will be back in 10 hours)

Ok, this is the last output. Thanks a lot and have a good rest.
andrea@andrea-Lenovo-Z50-75:~$ LANG=C sudo dpkg --configure -a
[sudo] password for andrea:
dpkg: dependency problems prevent configuration of python3-pyqt5.qtwebengine:
 python3-pyqt5.qtwebengine depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-pyqt5.qtwebengine (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of calibre:
 calibre depends on python3-pyqt5.qtwebengine (>= 5.12.1-4+b1); however:
  Package python3-pyqt5.qtwebengine is not configured yet.

dpkg: error processing package calibre (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of debconf-i18n:
 debconf-i18n depends on debconf (= 1.5.73); however:
  Version of debconf on system is 1.5.66ubuntu1.

dpkg: error processing package debconf-i18n (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-pyqt5:
 python3-pyqt5 depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-pyqt5 (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-html5-parser:
 python3-html5-parser depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-html5-parser (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-chm:
 python3-chm depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-chm (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-msgpack:
 python3-msgpack depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-msgpack (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-pyqt5.qtwebchannel:
 python3-pyqt5.qtwebchannel depends on python3-pyqt5 (= 5.14.1+dfsg-3build1); however:
  Package python3-pyqt5 is not configured yet.
 python3-pyqt5.qtwebchannel depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-pyqt5.qtwebchannel (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-pyqt5.qtsvg:
 python3-pyqt5.qtsvg depends on python3-pyqt5 (= 5.14.1+dfsg-3build1); however:
  Package python3-pyqt5 is not configured yet.
 python3-pyqt5.qtsvg depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-pyqt5.qtsvg (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-regex:
 python3-regex depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-regex (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-apsw:
 python3-apsw depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-apsw (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of backintime-qt:
 backintime-qt depends on python3-pyqt5; however:
  Package python3-pyqt5 is not configured yet.

dpkg: error processing package backintime-qt (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-debconf:
 python3-debconf depends on debconf (= 1.5.73); however:
  Version of debconf on system is 1.5.66ubuntu1.

dpkg: error processing package python3-debconf (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of systemd:
 systemd depends on libsystemd0 (= 245.4-4ubuntu3.3); however:
  Version of libsystemd0:amd64 on system is 237-3ubuntu10.43.

dpkg: error processing package systemd (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of backintime-qt4:
 backintime-qt4 depends on backintime-qt; however:
  Package backintime-qt is not configured yet.

dpkg: error processing package backintime-qt4 (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-sip:
 python3-sip depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-sip (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-dbus.mainloop.pyqt5:
 python3-dbus.mainloop.pyqt5 depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-dbus.mainloop.pyqt5 (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of onboard:
 onboard depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package onboard (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of python3-renderpm:amd64:
 python3-renderpm:amd64 depends on python3 (>= 3.8~); however:
  Version of python3 on system is 3.6.7-1~18.04.

dpkg: error processing package python3-renderpm:amd64 (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of systemd-timesyncd:
 systemd-timesyncd depends on systemd (= 245.4-4ubuntu3.3); however:
  Package systemd is not configured yet.

dpkg: error processing package systemd-timesyncd (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of libpam-systemd:amd64:
 libpam-systemd:amd64 depends on systemd (= 245.4-4ubuntu3.3); however:
  Package systemd is not configured yet.

dpkg: error processing package libpam-systemd:amd64 (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of libpolkit-qt5-1-1:amd64:
 libpolkit-qt5-1-1:amd64 depends on default-logind | logind; however:
  Package default-logind is not installed.
  Package libpam-systemd:amd64 which provides default-logind is not configured yet.
  Package logind is not installed.
  Package systemd-services which provides logind is not installed.
  Package libpam-systemd:amd64 which provides logind is not configured yet.

dpkg: error processing package libpolkit-qt5-1-1:amd64 (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of libkf5authcore5:amd64:
 libkf5authcore5:amd64 depends on libpolkit-qt5-1-1 (>= 0.113.0); however:
  Package libpolkit-qt5-1-1:amd64 is not configured yet.

dpkg: error processing package libkf5authcore5:amd64 (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of libkf5auth5:amd64:
 libkf5auth5:amd64 depends on libkf5authcore5 (= 5.68.0-0ubuntu1); however:
  Package libkf5authcore5:amd64 is not configured yet.

dpkg: error processing package libkf5auth5:amd64 (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of snapd:
 snapd depends on systemd; however:
  Package systemd is not configured yet.

dpkg: error processing package snapd (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of calibre-bin:
 calibre-bin depends on sip-py3api-12.7; however:
  Package sip-py3api-12.7 is not installed.
  Package python3-sip which provides sip-py3api-12.7 is not configured yet.

dpkg: error processing package calibre-bin (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of onboard-data:
 onboard-data depends on onboard (<< 1.4.1-2ubuntu7.1); however:
  Package onboard is not configured yet.
 onboard-data depends on onboard (>= 1.4.1-2ubuntu7); however:
  Package onboard is not configured yet.

dpkg: error processing package onboard-data (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of libkf5configwidgets5:amd64:
 libkf5configwidgets5:amd64 depends on libkf5authcore5 (>= 5.56.0); however:
  Package libkf5authcore5:amd64 is not configured yet.

dpkg: error processing package libkf5configwidgets5:amd64 (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of libkf5xmlgui5:amd64:
 libkf5xmlgui5:amd64 depends on libkf5configwidgets5 (>= 5.67.0); however:
  Package libkf5configwidgets5:amd64 is not configured yet.

dpkg: error processing package libkf5xmlgui5:amd64 (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 python3-pyqt5.qtwebengine
 calibre
 debconf-i18n
 python3-pyqt5
 python3-html5-parser
 python3-chm
 python3-msgpack
 python3-pyqt5.qtwebchannel
 python3-pyqt5.qtsvg
 python3-regex
 python3-apsw
 backintime-qt
 python3-debconf
 systemd
 backintime-qt4
 python3-sip
 python3-dbus.mainloop.pyqt5
 onboard
 python3-renderpm:amd64
 systemd-timesyncd
 libpam-systemd:amd64
 libpolkit-qt5-1-1:amd64
 libkf5authcore5:amd64
 libkf5auth5:amd64
 snapd
 calibre-bin
 onboard-data
 libkf5configwidgets5:amd64
 libkf5xmlgui5:amd64
andrea@andrea-Lenovo-Z50-75:~$ LANG=C sudo apt --fix-broken install
Reading package lists... Done
Building dependency tree
Reading state information... Done
Correcting dependencies... failed.
The following packages have unmet dependencies:
 bleachbit : Depends: python-gtk2 but it is not installable
             Recommends: python-notify but it is not installable
 debconf-i18n : Depends: debconf (= 1.5.73) but 1.5.66ubuntu1 is installed
 libnss-systemd : Depends: systemd (= 237-3ubuntu10.43)
 libqt4-declarative : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-designer : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-help : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-network : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-script : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-scripttools : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-sql : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-sql-sqlite : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-svg : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-test : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-xml : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqt4-xmlpatterns : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqtassistantclient4 : Depends: libqtcore4 (>= 4:4.8.1) but it is not installable
 libqtdbus4 : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 libqtgui4 : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 onboard : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python-dbus : Depends: python2 (< 2.8) but it is not installed
               Depends: python2 (>= 2.7~) but it is not installed
               Depends: python2:any (< 2.8)
               Depends: python2:any (>= 2.7~)
 python-gnucash : Depends: python-gtk2 but it is not installable
 python-libxml2 : Depends: python2 (< 2.8) but it is not installed
                  Depends: python2 (>= 2.7~) but it is not installed
                  Depends: python2:any (< 2.8)
                  Depends: python2:any (>= 2.7~)
 python-pil : Depends: python2 (< 2.8) but it is not installed
              Depends: python2 (>= 2.7~) but it is not installed
              Depends: python2:any (< 2.8)
              Depends: python2:any (>= 2.7~)
 python-pygments : Depends: python2:any (< 2.8)
                   Depends: python2:any (>= 2.7~)
 python-sip : Depends: python2 (< 2.8) but it is not installed
              Depends: python2 (>= 2.7~) but it is not installed
              Depends: python2:any (< 2.8)
              Depends: python2:any (>= 2.7~)
 python-xdg : Depends: python2:any (< 2.8)
              Depends: python2:any (>= 2.7~)
 python3 : PreDepends: python3-minimal (= 3.6.7-1~18.04) but 3.8.2-0ubuntu2 is installed
           Depends: libpython3-stdlib (= 3.6.7-1~18.04) but 3.8.2-0ubuntu2 is installed
 python3-apsw : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-chm : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-dbus.mainloop.pyqt5 : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-dbus.mainloop.qt : Depends: libqtcore4 (>= 4:4.8.0-1~) but it is not installable
 python3-debconf : Depends: debconf (= 1.5.73) but 1.5.66ubuntu1 is installed
 python3-html5-parser : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-msgpack : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-pyqt4 : Depends: libqtcore4 (>= 4:4.8.0-1~) but it is not installable
 python3-pyqt5 : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-pyqt5.qtsvg : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-pyqt5.qtwebchannel : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-pyqt5.qtwebengine : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-regex : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-renderpm : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 python3-sip : Depends: python3 (>= 3.8~) but 3.6.7-1~18.04 is installed
 qdbus : Depends: libqtcore4 (= 4:4.8.7+dfsg-7ubuntu1) but it is not installable
 qt-at-spi : Depends: libqtcore4 (>= 4:4.8~) but it is not installable
 sni-qt : Depends: libqtcore4 (>= 4:4.7.3-1ubuntu3~) but it is not installable
          Depends: libdbusmenu-qt2 but it is not installable
 systemd : Depends: libsystemd0 (= 245.4-4ubuntu3.3) but 237-3ubuntu10.43 is installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.
E: Unable to correct dependencies
andrea@andrea-Lenovo-Z50-75:~$

What output do you receive for the commands

ubuntu-support-status
ubuntu-security-status

Welcome back Manfred and one more thank for your support.Her's the last output:
andrea@andrea-Lenovo-Z50-75:~$ ubuntu-support-status
Traceback (most recent call last):
  File "/usr/lib/command-not-found", line 28, in <module>
    from CommandNotFound import CommandNotFound
  File "/usr/lib/python3/dist-packages/CommandNotFound/CommandNotFound.py", line 19, in <module>
    from CommandNotFound.db.db import SqliteDatabase
  File "/usr/lib/python3/dist-packages/CommandNotFound/db/db.py", line 5, in <module>
    import apt_pkg
ModuleNotFoundError: No module named 'apt_pkg'
andrea@andrea-Lenovo-Z50-75:~$ ubuntu-security-status
Traceback (most recent call last):
  File "/usr/bin/ubuntu-security-status", line 3, in <module>
    import apt
  File "/usr/lib/python3/dist-packages/apt/__init__.py", line 23, in <module>
    import apt_pkg
ModuleNotFoundError: No module named 'apt_pkg'
andrea@andrea-Lenovo-Z50-75:~$

It seems that the release upgrade was interrupted at the worst possible moment. During the upgrade from Ubuntu 18.04 to 20.04 several packages have to be updated to newer versions, and due to significant changes in the python version between these two releases most python-dependent packages from ubuntu 18.04 do not work with the python version of Ubuntu 20.04 and vice versa. Apparently your system now is in a status that half of the python-dependent packages are on the level of Ubuntu 18.04 and half are on 20.04, such that most of them are not working. My assumption is that this can only be repaired by either manually upgrading all packages to the version fitting to Ubuntu 20.04, or by reverting all of them to Ubuntu 18.04 level (and then doing a new upgrade to 20.04). This will probably be a long way to go.

Do you see the chance to do a complete new installation? This might be far easier. The only thing to consider is saving the files that you deem worth being kept. There are some possibilities - installing a backup tool (which seems hardly possible in the moment), or just inserting an external storage medium like an USB stick or a USB hard disk and copying the files there.

What do you think?

Thank you for your clarity, Manfred. Actually my first idea was to backup it all and then reinstall Ubuntu 20.04. But neither the backup application nor the update one weren't working. So the option would be to manually back up on an external hd and then create a bootable pendrive to reinstall, isn't it? What is the risk of loosing data about? Any kind of file (documents, sw, etc.)? Because actually the application I would need to upgrade are not many: Back in time, Calibre essentially.

You have to distinguish data and applications. There should not be any need to make a backup copy of the Calibre program, because it can easily be reinstalled from the standard repositories when the operating system is correctly working. What you have to care for are the books that you are reading with Calibre. They have to be saved elsewhere. When doing a new installation, everything on the hard disk partitions will be deleted, so you have to care for creating backup copies of the document, music files, e-books, etc. - whatever you currently have stored on your computer.

First step is checking your system - where are the files that should be kept? What is the approximate total size (will they fit on a pen drive)?

If you have made lots of modifications to the settings (e.g. desktop background images, screen color, sounds, etc.) then you have also think on these data, if you want to apply similar settings also on the new installation.

Hi Manfred, I downloaded an iso image of Ubuntu-20.04.1 desktop amd64 and tried to burn it into a pen, then to boot it but the pen doesn't boot. Maybe the problem is related to the application I used wich isn't working properly.
I also downloaded a second iso file on my hd to try to burn it with dd application from terminal window but I got an error message.
What can I do to have a working bootable pendrive?

Which operating system do you have available?
There are instructions for Ubuntu, Windows and MacOS on the bottom of https://ubuntu.com/download/desktop

How to create a bootable USB stick on Ubuntu
How to create a bootable USB stick on Windows
How to create a bootable USB stick on macOS

For Ubuntu you should use the application "Startup Disk Creator"

I have Ubuntu 20.04 partially installed but many application are not running

But I'm not able to launch Startup disk creator from the applications window

What happens if you issue the command

usb-creator-gtk

Does it fail with messages from python?

There is the possibility to copy with the dd command. The command should look like this:

sudo dd bs=4M if=path/to/input.iso of=/dev/sd<?> conv=fdatasync status=progress

Replace /dev/sd<?> by the name that has been assigned to the pendrive by the system, probably /dev/sdb
But before starting the command make sure that the system hasn't automatically mounted the partition(s) of he thumb drive
sudo umount /dev/sdb1
sudo umount /dev/sdb2

andrea@andrea-Lenovo-Z50-75:~$ usb-creator-gtk
Traceback (most recent call last):
  File "/usr/bin/usb-creator-gtk", line 22, in <module>
    from dbus import DBusException
  File "/usr/lib/python3/dist-packages/dbus/__init__.py", line 77, in <module>
    import dbus.types as types
  File "/usr/lib/python3/dist-packages/dbus/types.py", line 6, in <module>
    from _dbus_bindings import (
ModuleNotFoundError: No module named '_dbus_bindings'
andrea@andrea-Lenovo-Z50-75:~$

The pendrive seems to have all the ubuntu 20.04 sw but doesn't boot when I restart the pc with it inserted.
Does the dd command burn the bootable pendrive starting fro the iso file?

If you do it correctly, then the pendrive should be bootable.
What boot priority is set in the BIOS of your computer?
You have to (temporarily) give USB devices a higher priority than the built-in hard disk.

How can I see that?
And how do I do it if I need to change it?

Reboot your computer, and very early during the boot process you usually see a logo of your computer's manufacturer and some text like "press F10 for setup" or "press F12 for boot device" or something similar.

Just do that to enter BIOS setup mode and try identifying the relevant entries on screen.

Hi Manfred, I tried to do it pressing F2, F10 and F12 with no result and also ESC that led me to the possibility to enter the recovery mode but didn't find an option to reinstall Ubuntu.
If I access the USB Flash drive I see what follows:

Model: Lexar USB Flash drive(1100)
Dimension: 16 GB
Partition: Master Boot Record
Serial number: AA2UGA89D5BNL76H
Volumes:
Partition 1
Ubuntu 20.04.1 LTS amd64
Dimension 2,8 GB
Device /dev/sdb1
UUID 2020-07-31-16-51-12-00
Partition type 0x00 (bootable)
Content ISO 9660 (version Joilet Extension) ---Mounted on /media/andrea/Ubuntu 20.04.1 LTS amd 64

Partition 2
Ubuntu 20.04.1 LTS amd64
Dimension 4,1 MB
Device /dev/sdb2
UUID C26E-047E
partition type EFI (FAT-12/16/32)
Content FAT (version 12 bit) ---Unmounted

Partition 3
Free space
Dimension 13 GB
Device /dev/sdb
Content Not allocated space

Is there a way to see and modify the Bios fron terminal window?
Thanks

If pressing ESC leads to the grub menu with a selection possibility of recovery mode - then this is too late. YOU have to press the key earlier.
What make and model is you system? There are web pages with lists of the keys to press (could also be F3).

It's a Lenovo Z50-75.
I tried pressing every function key before reboot start and kept it pressed all time of scrolling. Didn't try with F3 but I will.

No result

see https://support.lenovo.com/us/en/videos/vid100750
(the Windows specific options will not be applicable)

When you boot, do you see a "Lenovo" logo on screen very early during the boot sequence?

Yes, but Windows was erased before installing Ubuntu

When you see that Lenovo logo during the boot process, is there additional text on screen?

Hi Manfred,

I did it finally, I installed the new version! Thanks a lot for all of your support!

Andrea

Thanks Manfred Hampl, that solved my question.