Created attachment 126980 [details]
`journalctl -b-1` output during the next session after the freeze occured

SUMMARY
The system freezes unrecoverably, seemingly at random intervals, but usually within about 30 minutes after startup.
I have a feeling I'm experiencing a very unique issue, and have not been able to find any type of bug report, forum post, or other type of content on the web that exactly matches my problem.


STEPS TO REPRODUCE
1. I just run a normal KDE plasma instance, and then eventually it freezes (usually after about 30 minutes, but this is inconsistent).


OBSERVED RESULT
The system freezes and there is nothing that I can do except to hard-reset my PC. SysRq doesn't work, switching to a different TTY doesn't work, nothing. The system just stops. Interestingly, when this happens, the screen still displays the last frame that was rendered. The crash can "only" be noticed since the screen doesn't update, and inputs don't have any effect.


EXPECTED RESULT
The system doesn't freeze :)


SOFTWARE/OS VERSIONS
Linux: 5.5.11-arch1-1 #1 SMP PREEMPT Sun, 22 Mar 2020 16:33:15 +0000 x86_64 GNU/Linux
KDE Plasma Version: 5.18.3
KDE Frameworks Version: 5.68.0
Qt Version: 5.14.1

Root-Filesystem: btrfs

ADDITIONAL INFORMATION
Hardware:
 - CPU: AMD Ryzen 5 3600X
 - GPU: AMD Radeon RX 5700 XT
 - RAM: 32 GB DDR4
 - Motherboard: B450 Aorus Elite

I have AMD microcode updates installed (amd-ucode Arch Linux package). I have mesa and xf86-video-amdgpu packages installed.

The bug also occurs when:
 - I run KDE without a compositor (disabled at startup)
 - I run a different kernel (Arch Linux's linux-lts kernel)
 - I create a new user, and log into a Plasma session without any customizations at all

The bug does not occur when:
 - I run i3 instead of KDE (I ran an i3 session overnight and it didn't freeze)
 - I boot into a terminal and don't run any kind of graphical interface

Things I haven't tried yet:
 - Run a different DE that is maybe more comparable to KDE than i3 (e.g. Gnome)
 - Run a Wayland session of KDE (tried that, couldn't really get it to work -- it started, but a bunch of Plasma components didn't want to play along, so I abandoned that approach)
 - Use a different GPU (I have an older Nvidia GPU lying around here somewhere that I could try to use instead of the Radeon card)

I've noticed that the last entries in journalctl seem to be related to kwin_x11 -- I'll attach a full system log from a session where the freeze occured. Maybe it'll help. Note that there seems to be about a minute between the last log entry and the actual freeze...

I'll be happy to provide any and all kinds of additional information that I can.

I'm really at the end of my knowledge here. I suppose it may not be directly a KDE/Plasma bug -- it could be caused by some weird hardware issue that just happens to be triggerd by Plasma and not by i3 or something like that. But maybe someone here will be able to help. Many thanks in advance for any input!