I researched this problem here and on Google but didn't come up with a solution this far.
I'm using Ubuntu 18.04.4 and have a massive problem with random screen freezes. I can't pinpoint it to any program but it seems to appear more often when using Firefox for browsing, but in general, it can appear when I do nothing on the desktop. The screen freezes but I can move the mouse pointer (it also changes appearance for hyperlinks and stuff like that) but the screen doesn't refresh. Audio will play on (for instance while watching a movie). I can login again using Ctrl+Alt+F1 but sometimes it takes only seconds until the screen freezes again.
Here some random logs that might help, if you need more info, let me know. Any help is appreciated!
free -h
Gesamt belegt frei gemns. Puffer/Cache verfügbar
Speicher: 3,8G 1,9G 173M 146M 1,7G 1,5G
Auslagerungsspeicher: 3,9G 1,0M 3,9G
lspci | grep VGA
07:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Barts XT [Radeon HD 6870]
Update: I tried adding the acpi_rev_override=1 argument to splash in /etc/default/grub which didn't work. A change in the Bios graphics settings for the graphics to be "discrete" isn't existing in my Bios.