Whenever I wake my computer after the screen turned off, the screen is frozen on the login panel for about 30 seconds before it flickers black, at which point it will wake up again and let me type my password to log in. Sometimes the panel will display “timed out” before the screen flickers to black.
I am running Ubuntu Budgie 20.04LTS. I have an AMD RX570 graphics card and dual monitors.
This same thing started happening to me just today. I was hoping to get a clue what’s causing it. The only recent changes are regular updates. In my case, I get the login screen for a second then it blanks. The system seems to be running. After fooling around striking keys and wiggling the mouse, I eventually give up and hit the power switch. It’s pretty annoying. It happened the last two times the screen blanked after a timeout. I’m not sure how long the timeout has to last or if that’s a factor. If it happens again I’ll try a VNC remote connection to see if that’s blank as well. If there’s a better idea I’d be glad to learn it.
Have you tried to reach a tty/virtual console? (CTRL+ALT+F2, up to F6)
If your computer is not actually frozen, from there you can check if your system is at least still running and eventually kill your X and/or gdm session, which will in turn respawn gdm/lightdm for a new GUI session without rebooting.
This didn’t get a lot of attention but I’ll add a quick follow up. Sort of a 'doh! moment.
My problem was my monitor. It quit. It didn’t occur to me that it would quit by failing intermittently. I figured out a keyboard shortcut sequence that I could use (without being able to see the desktop) to log in (if the lock screen was on), make sure that the focus was on the desktop (so no open window would take the keyboard shortcut I was using) and lock the screen again. This had the effect of goosing the display and it would return to normal for a while. I could log on and it might not happen again for days or a week. I figured something in the OS had gone buggy.
Nope. It started happening more often then then, all at once, the display would blank after a couple of seconds over and over no matter what I did. I switched monitors and 'doh! It was the monitor. It took me a long time to ask - could it be the monitor? It’s always in the last place you look.