I can only guess. gdm3 will usually run the login screen on VT1 only. The second login screen on VT3 may be either a pure mistake (gdm3 not knowing what is current at the time), or it might be a fallback if changing to VT1 briefly wasn't possible (for some reason). Either way it's failing to clean up.
I suggest the next step is to report the bug to the gdm developers here: https://gitlab.gnome.org/GNOME/gdm And when done please let us know the new bug ID. ** Changed in: gdm3 (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gdm3 in Ubuntu. https://bugs.launchpad.net/bugs/1809660 Title: When starting new user session, new gdm session may spawn To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1809660/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
