Issues after suspend/resume, SDDM blank, Plasma frozen

General system Kernel, boot, graphics & hardware
1

Has anyone else seen issues like this one? I’ve been stumped on it for a while now.
Short version: when my PC’s screen turns off (whether from the idle timer in Plasma or the sleep button), things are broken the next time I wake it up.

  • First, SDDM shows an all-black screen except for the mouse cursor. It does respond to input, I could type my password and unlock while driving blind. Notably, if I turn the image off and on several times (hit escape to cancel unlock and then wake it again, or switch to a TTY and back), sometimes it’ll fix itself and start drawing the UI again.
  • Second, Plasma Shell is frozen upon unlock. Inputs work still, most apps still work, but the panels and system-wide keyboard shortcuts like alt-tab do not. Panels do render, but are non-interactive, and the wallpaper is blank, but desktop icons do render. Sometimes it’ll sorta restart, throwing a notification like “desktop effects have been reset” or something. Other times the issue persists until I reboot.
  • Sometimes other apps are frozen similarly to Plasma, like Discord, or the web browser. But for these, the problem rights itself in a similar way relatively quickly.

I’m not really sure how to begin diagnosing the issue, honestly. I have a few more specific questions, but I can’t tell if this is an X/Y problem.

  • How do I tell which form of suspend I’m using? Arch wiki > Power Management > Suspend lists four methods: IdleS2Idle, Suspend to RAM, Hibernate, Hybrid Sleep. The only thing I know for sure is that I don’t have the Hibernate option in the GUI, and I’m pretty sure that I don’t have any swap space? No mention of swap in /etc/fstab, no swap partition…
  • I wonder if it’s related to my version of the Nvidia drivers? I’m currently using nvidia-open-dkms as it’s what nvidia-inst says is recommended for Turing and later… I would try Nouveau just because, but when I do it says there’s problems related to dependencies.
  • I did get some search hits suggesting something related to Nvidia and kernel parameters, but nothing changed. My current parameter string (formatted for reading):
# /etc/kernel/cmdline
initrd=\[...]\6.14.4-arch1-1\initrd
nowatchdog
nvidia_drm.modeset=1
nvidia.NVreg_PreserveVideoMemoryAllocations=1
nvidia.NVreg_TemporaryFilePath=/var/tmp
nvme_load=YES
rootflags=subvol=/@
root=UUID=[...]
rw
systemd.machine_id=[...]

Setup:

  • GPU: Nvidia GTX 1650 Super
  • Motherboard: ASRock B450M Pro4
  • CPU: AMD Ryzen 5 2600 Six-Core Processor
  • Display Manager: SDDM
  • DE: KDE Plasma
  • Happens whether in X11 or Wayland.

Is there any other info that would help here?