I installed Ubuntu 20.04.3 (Gnome version 3.36.8) on two different systems (one desktop, one laptop). On both systems after the first boot the login manager does not come up and I have to login via tty
and do startx.
When I log out, I can log in with gdm3 again but when the laptop goes into power saving mode the session usually crashes.
The installs are independent (different downloads, sticks, both verified with shasum). It is not an upgrade from an older version like in gdm3 not starting on ubuntu 20.04 and the /usr/share/glib-2.0/schemas/org.gnome.mutter.x11.gschema.xml file does not seem to be broken like indicated in the resolution in of this bug report.
It also does not seem to be related to Ubuntu doesn't start gdm3 and enters tty1 on boot since this output seems correct:
> systemctl get-default
graphical.target
Setting WaylandEnable=false in /etc/gdm3/custom.conf like suggested in GDM3 does not start in Ubuntu 18.04 also does not seem to help.
I don't know enough about GNOME to know what further information to include, so please let me know.
> systemctl status gdm
● gdm.service - GNOME Display Manager
Loaded: loaded (/lib/systemd/system/gdm.service; static; vendor preset: enabled)
Active: active (running) since Tue 2022-01-11 10:29:18 CET; 2h 5min ago
Main PID: 843 (gdm3)
Tasks: 3 (limit: 9400)
Memory: 3.7M
CGroup: /system.slice/gdm.service
└─843 /usr/sbin/gdm3
Jan 11 10:29:28 sam-desktop gdm3[843]: Child process -1515 was already dead.
Jan 11 10:29:28 sam-desktop gdm3[843]: Child process -1515 was already dead.
Jan 11 10:29:28 sam-desktop gdm-launch-environment][1610]: pam_unix(gdm-launch-environment:session): s>
Jan 11 10:29:31 sam-desktop gdm3[843]: GdmDisplay: Session never registered, failing
Jan 11 10:29:31 sam-desktop gdm3[843]: Child process -1617 was already dead.
Jan 11 10:29:31 sam-desktop gdm3[843]: Child process -1617 was already dead.
Jan 11 10:29:31 sam-desktop gdm-launch-environment][1742]: pam_unix(gdm-launch-environment:session): s>
Jan 11 10:29:33 sam-desktop gdm3[843]: GdmDisplay: Session never registered, failing
Jan 11 10:29:33 sam-desktop gdm3[843]: GdmLocalDisplayFactory: maximum number of X display failures re>
Jan 11 10:29:33 sam-desktop gdm3[843]: Child process -1749 was already dead.
One thing to mention is that (sadly) both systems run on a nvidia graphics card which as indicated in this answer could be a problem.
Edit: I just like to add that I am aware that using lightdm is another possible solution but I'd prefer to continue using gdm3.
