Comment 2 for bug 1872123

I am having a similar issue. My graphics card is a Geforce GTX 1060 and the kernel is 5.4.0-21. By default, Ubuntu 20.04 was using `nouveau` drivers, but nouveau doesn't behave well with some applications I need, in particular RStudio (which tends to crash under nouveau).

So, I enabled NVidia 440 series proprietary drivers through Software and Updates. Then, I rebooted.

First odd thing: I rebooted into GDM while normally auto-login is enabled. I should have been auto-logged into my default session, which is Gnome on Xorg (not Ubuntu default) but I wasn't.

Second odd thing: the little gear at the bottom right corner of GDM - used to switch desktop session - was gone.

Third odd thing: after I typed my password into GDM, nothing happened. At all. Not even a flicker.

So I switched to a virtual console, logged in and entered `startx`. Screen went black for an instant, then I was back to the console with a brief log output telling me that X had successfully stopped.

I rebooted, same issue. So, I rebooted again, but in GRUB I picked Advanced Options, then Rescue Mode, then Resume boot as normal in the ncurse box. This time, I was automatically logged in to my default session (GNOME on Xorg, not Ubuntu).

I logged out to GDM. Now, the session gear is back in the corner of the screen... However, Wayland sessions are no longer listed - maybe this is a default behavior when NVidia proprietary drivers are enabled since Wayland support isn't exactly spot on yet?

Anyway, if you're having this problem too, the workaround is a rescue boot from GRUB. Then, you can either re-enable nouveau or get used to rescue booting... But this can only be a temporary solution.