How to remove impish-security Release from Ubuntu 22.04?

Ubuntu Impish Indri was release 21.10 and is not supported any more (since July 14, 2022, see https://wiki.ubuntu.com/Releases )
You have to remove all references to that release from your package management configuration.

For diagnostic purposes please provide the output that you receive for the following commands (to be executed in a terminal window):

uname -a
lsb_release -crid
find /etc/apt -name '*.list' -exec bash -c 'echo -e "\n$1\n"; cat -n "$1"' _ '{}' \;

michael@michael-Inspiron-620:~$ uname -a
Linux michael-Inspiron-620 5.15.0-50-generic #56-Ubuntu SMP Tue Sep 20 13:23:26 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

michael@michael-Inspiron-620:~$ lsb_release -crid
Distributor ID: Ubuntu
Description: Ubuntu 22.04.1 LTS
Release: 22.04
Codename: jammy

michael@michael-Inspiron-620:~$ find /etc/apt -name '*.list' -exec bash -c 'echo -e "\n$1\n"; cat -n "$1"' _ '{}' \;

/etc/apt/sources.list.d/opera-stable.list

     1 # This file makes sure that Opera Browser is kept up-to-date
     2 # as part of regular system upgrades
     3
     4 # deb https://deb.opera.com/opera-stable/ stable non-free #Opera Browser (final releases) disabled on upgrade to jammy

/etc/apt/sources.list.d/google-chrome.list

     1 ### THIS FILE IS AUTOMATICALLY CONFIGURED ###
     2 # You may comment out this entry, but any other modifications may be lost.
     3 # deb [arch=amd64] https://dl.google.com/linux/chrome/deb/ stable main

/etc/apt/sources.list

     1 # deb cdrom:[Ubuntu 21.10 _Impish Indri_ - Release amd64 (20211012)]/ impish 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://us.archive.ubuntu.com/ubuntu/ jammy main restricted
     6 # deb-src http://us.archive.ubuntu.com/ubuntu/ impish main restricted
     7
     8 ## Major bug fix updates produced after the final release of the
     9 ## distribution.
    10 deb http://us.archive.ubuntu.com/ubuntu/ jammy-updates main restricted
    11 # deb-src http://us.archive.ubuntu.com/ubuntu/ impish-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://us.archive.ubuntu.com/ubuntu/ jammy universe
    17 # deb-src http://us.archive.ubuntu.com/ubuntu/ impish universe
    18 deb http://us.archive.ubuntu.com/ubuntu/ jammy-updates universe
    19 # deb-src http://us.archive.ubuntu.com/ubuntu/ impish-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://us.archive.ubuntu.com/ubuntu/ jammy multiverse
    27 # deb-src http://us.archive.ubuntu.com/ubuntu/ impish multiverse
    28 deb http://us.archive.ubuntu.com/ubuntu/ jammy-updates multiverse
    29 # deb-src http://us.archive.ubuntu.com/ubuntu/ impish-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 deb http://us.archive.ubuntu.com/ubuntu/ jammy-backports main restricted universe multiverse
    37 # deb-src http://us.archive.ubuntu.com/ubuntu/ impish-backports main restricted universe multiverse
    38
    39
    40 deb http://security.ubuntu.com/ubuntu jammy-security main restricted
    41 deb-src http://security.ubuntu.com/ubuntu impish-security main restricted
    42 deb http://security.ubuntu.com/ubuntu jammy-security universe
    43 deb-src http://security.ubuntu.com/ubuntu impish-security universe
    44 deb http://security.ubuntu.com/ubuntu jammy-security multiverse
    45 deb-src http://security.ubuntu.com/ubuntu impish-security multiverse
    46
    47 # This system was installed using small removable media
    48 # (e.g. netinst, live or single CD). The matching "deb cdrom"
    49 # entries were disabled at the end of the installation process.
    50 # For information about how to configure apt package sources,
    51 # see the sources.list(5) manual.

Numbers 47 48 NOT true. This installation was an upgrade.

I have only used the upgrade (from 21.10) and updates and Synaptic Package manager. No downloads from any other source.

How did N. B. software get into repository?

(From https://en.wikipedia.org/wiki/Nota_bene, N.B. in short means "pay attention" or "take notice". Therefore, the comment is telling you you should take note the software in that repository is not supported by Ubuntu.)

I put in your command. sudo gedit /etc/apt/sources.list
The editor window came up, I changed impish to jammy. Put # in front of 41 and 43, there was no 54. Only went to 51. When I hit save, the below was in the terminal.

michael@michael-Inspiron-620:~$ sudo gedit /etc/apt/sources.list
[sudo] password for michael:

** (gedit:13521): WARNING **: 13:18:10.276: Set document metadata failed: Setting attribute metadata::gedit-spell-language not supported

** (gedit:13521): WARNING **: 13:18:10.277: Set document metadata failed: Setting attribute metadata::gedit-encoding not supported

Will reopen terminal and run sudo apt update. No way to run it in the terminal now.

michael@michael-Inspiron-620:~$ sudo apt update
[sudo] password for michael:
Hit:1 http://us.archive.ubuntu.com/ubuntu jammy InRelease
Get:2 http://us.archive.ubuntu.com/ubuntu jammy-updates InRelease [114 kB]
Get:3 http://security.ubuntu.com/ubuntu jammy-security InRelease [110 kB]
Get:4 http://us.archive.ubuntu.com/ubuntu jammy-backports InRelease [99.8 kB]
Get:5 http://us.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages [662 kB]
Get:6 http://us.archive.ubuntu.com/ubuntu jammy-updates/main i386 Packages [344 kB]
Get:7 http://us.archive.ubuntu.com/ubuntu jammy-updates/main amd64 DEP-11 Metadata [93.0 kB]
Get:8 http://us.archive.ubuntu.com/ubuntu jammy-updates/main amd64 c-n-f Metadata [9,404 B]
Get:9 http://us.archive.ubuntu.com/ubuntu jammy-updates/universe i386 Packages [283 kB]
Get:10 http://us.archive.ubuntu.com/ubuntu jammy-updates/universe amd64 Packages [435 kB]
Get:11 http://security.ubuntu.com/ubuntu jammy-security/multiverse Sources [4,628 B]
Get:12 http://us.archive.ubuntu.com/ubuntu jammy-updates/universe amd64 DEP-11 Metadata [247 kB]
Get:13 http://us.archive.ubuntu.com/ubuntu jammy-updates/multiverse amd64 DEP-11 Metadata [940 B]
Get:14 http://us.archive.ubuntu.com/ubuntu jammy-backports/universe amd64 DEP-11 Metadata [12.6 kB]
Get:15 http://us.archive.ubuntu.com/ubuntu jammy-backports/universe amd64 c-n-f Metadata [356 B]
Get:16 http://security.ubuntu.com/ubuntu jammy-security/main amd64 DEP-11 Metadata [20.0 kB]
Get:17 http://security.ubuntu.com/ubuntu jammy-security/universe amd64 DEP-11 Metadata [13.3 kB]
Fetched 2,451 kB in 1s (2,180 kB/s)
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
All packages are up to date.

Thanks Manfred Hampl, that solved my question.

Manfred Hampl
You were right, I did download programs (Opera). My bad.
Thank You very much for your answer!

Sorry for my typo, should have been
In line 41, 43 and 45 ...

" No way to run it in the terminal now."
I assume, you did not close the editor program. That blocks the terminal where you started it.

"the below was in the terminal."
That's normal and does not do any harm.

Hey Manfred!
Now that you helped me fix my internet connection, I wonder if you could help me update to Ubuntu 22.10. I keep getting similar errors to those in this thread, but I tried all the steps listed here with no luck. I also tried other solutions I found online with no luck there either. Would you be able to help me troubleshoot it?
Thanks!
Sam

Here's the most recent error I received when trying to update from the GUI: W:Updating from such a repository can't be done securely, and is therefore disabled by default., W:See apt-secure(8) manpage for repository creation and user configuration details., E:The repository 'https://packagecloud.io/AllToMP3/alltomp3/ubuntu jammy Release' does not have a Release file., W:Updating from such a repository can't be done securely, and is therefore disabled by default., W:See apt-secure(8) manpage for repository creation and user configuration details., W:The repository 'http://old-releases.ubuntu.com/ubuntu jammy Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., W:Target Sources (restricted/source/Sources) is configured multiple times in /etc/apt/sources.list:2 and /etc/apt/sources.list:7, W:Target Sources (main/source/Sources) is configured multiple times in /etc/apt/sources.list:2 and /etc/apt/sources.list:7, W:The repository 'http://old-releases.ubuntu.com/ubuntu jammy-updates Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., W:The repository 'http://old-releases.ubuntu.com/ubuntu jammy-backports Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., W:The repository 'http://old-releases.ubuntu.com/ubuntu jammy-security Release' does not have a Release file.

@Sam Lane: Do not piggyback on somebody else's question that has already been marked as "solved", but create a question document of your own.

Oh okay, sorry about that! A lot of other forums don’t want people creating threads if there is already one about the given topic. But thanks for letting me know about the standard here. I’ll create a new thread.