Comment 3 for bug 2039378

Am experiencing a similar issue which may be the same bug.

OS: Ubuntu 20.04
Kernel: 5.15.0-86-generic
Desktop: GNOME
Graphics: AMD

Just before/after logging in, the screen flickers and/or goes blank. Attempting to switch to a terminal using Ctrl+Alt+F-keys doesn't help. Attempting to restart using Ctrl+Alt+Del doesn't work.

Choosing the previous kernel (5.15.0-84-generic) from the GRUB menu instead, when booting, avoids the issue.

Other reports of similar sounding issues:
https://askubuntu.com/questions/1488418/ubuntu-20-04-screen-artifacts-during-login
https://forums.linuxmint.com/viewtopic.php?t=405762