After an upgrade yesterday:
Dec 14 09:04:38 defiant systemd[1]: Starting gdm.service - GNOME Display Manager…
Dec 14 09:04:38 defiant systemd[1]: Started gdm.service - GNOME Display Manager.
Dec 14 09:04:38 defiant gdm3[2505]: Gdm: Failed to listen on userdb socket: Invalid argument
Any ideas how to fix? gdm3 fails to start = no GUI
Same for me on 2 different partitions with 26.04
Installed on a different partition from ISO dated Dec 12 and updated excluding gdm3 the system boots ok
sudo apt-mark hold gdm3
Updated fix of gdm3 has been released and applied after running
sudo apt-mark unhold gdm3
Thanks for the quick “resolution” 
I have two test computers, one with Nvidia graphics and one with Radeon graphic.
To do an install with USB on the computer with Radeon graphic works fine, but on the computer with Nvidia graphic, the installation of 26.04 will not start. I suppose this is related to the Geforce RTX 5060 Ti I’m using.
Yesterday I decided to use “sudo do-release-upgrade -d”
