On login screen after my user i see 'not listed?' what is it?

What is the output of:

lsb_release -a; uname -a; apt-cache policy gdm lightdm

Thanks

corrado@corrado-x4-ff-beta:~$ lsb_release -a; uname -a; apt-cache policy gdm lightdm
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu Focal Fossa (development branch)
Release: 20.04
Codename: focal
Linux corrado-x4-ff-beta 5.4.0-21-generic #25-Ubuntu SMP Sat Mar 28 13:10:28 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
gdm:
  Installed: (none)
  Candidate: (none)
  Version table:
lightdm:
  Installed: (none)
  Candidate: 1.30.0-0ubuntu3.1
  Version table:
     1.30.0-0ubuntu3.1 500
        500 http://archive.ubuntu.com/ubuntu focal/universe amd64 Packages
corrado@corrado-x4-ff-beta:~$

Note: the same thing happens on various installations of Ubuntu 19.10 and 20.04 on different hardware.

corrado@corrado-x4-ff-beta:~$ inxi -Fxx
System: Host: corrado-x4-ff-beta Kernel: 5.4.0-21-generic x86_64 bits: 64 compiler: gcc
           v: 9.3.0 Desktop: Gnome 3.36.0 wm: gnome-shell dm: GDM3
           Distro: Ubuntu 20.04 LTS (Focal Fossa)
Machine: Type: Desktop Mobo: ASRock model: H110M-G/M.2 serial: <superuser/root required>
           UEFI: American Megatrends v: P1.10 date: 05/11/2017
CPU: Topology: Dual Core model: Intel Core i3-7100 bits: 64 type: MT MCP arch: Kaby Lake
           rev: 9 L2 cache: 3072 KiB
           flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx bogomips: 31199
           Speed: 801 MHz min/max: 800/3900 MHz Core speeds (MHz): 1: 800 2: 801 3: 800 4: 800
Graphics: Device-1: Intel HD Graphics 630 vendor: ASRock driver: i915 v: kernel
           bus ID: 00:02.0 chip ID: 8086:5912
           Display: x11 server: X.Org 1.20.7 driver: i915 compositor: gnome-shell
           resolution: 1920x1080~60Hz
           OpenGL: renderer: Mesa Intel HD Graphics 630 (KBL GT2) v: 4.6 Mesa 20.0.2
           direct render: Yes
Audio: Device-1: Intel 100 Series/C230 Series Family HD Audio vendor: ASRock
           driver: snd_hda_intel v: kernel bus ID: 00:1f.3 chip ID: 8086:a170
           Device-2: Logitech QuickCam Pro 9000 type: USB driver: snd-usb-audio,uvcvideo
           bus ID: 1-10:5 chip ID: 046d:0990
           Sound Server: ALSA v: k5.4.0-21-generic
Network: Device-1: Intel Ethernet I219-V vendor: ASRock driver: e1000e v: 3.2.6-k port: f040
           bus ID: 00:1f.6 chip ID: 8086:15b8
           IF: enp0s31f6 state: up speed: 100 Mbps duplex: full mac: 70:85:c2:44:7b:86
Drives: Local Storage: total: 2.05 TiB used: 10.20 GiB (0.5%)
           ID-1: /dev/nvme0n1 vendor: Kingston model: SKC2000M8250G size: 232.89 GiB
           speed: 31.6 Gb/s lanes: 4 serial: 50026B72823D1475
           ID-2: /dev/sda vendor: Toshiba model: DT01ACA100 size: 931.51 GiB speed: 6.0 Gb/s
           serial: 37PYNGAFS
           ID-3: /dev/sdb vendor: Hitachi model: HDS721010CLA332 size: 931.51 GiB
           speed: 3.0 Gb/s serial: JP2940J80Z3D3V
Partition: ID-1: / size: 31.25 GiB used: 10.20 GiB (32.6%) fs: ext4 dev: /dev/nvme0n1p4
           ID-2: swap-1 size: 8.00 GiB used: 0 KiB (0.0%) fs: swap dev: /dev/sda2
Sensors: System Temperatures: cpu: 45.0 C mobo: N/A
           Fan Speeds (RPM): N/A
Info: Processes: 208 Uptime: 33m Memory: 7.49 GiB used: 1.67 GiB (22.3%) Init: systemd
           v: 245 runlevel: 5 Compilers: gcc: N/A Shell: bash v: 5.0.16
           running in: gnome-terminal inxi: 3.0.38
corrado@corrado-x4-ff-beta:~$

Just checked: same happens on various installations of Ubuntu 18.04 on 3 different hardware.
All systems are just installed from the ISO and not customized at all.

Thanks Manfred Hampl, that solved my question.