I have similar issues to report, I have a feeling this is 6.15.4 regression, HDMI was a bit more stable before the latest update, now it’s barely usable.
- I’m on Sway as well, my external screen is QHD, I’ll test on FHD tomorrow
- Plugging HDMI when Pocket is working twice resulted in a reboot, like power cycle (Pocket screen quickly dimmed without change in picture), other times it’s fine
- Unplugging HDMI didn’t give me freezes or reboots
- Bizarrely, external display blinks all the time ONLY when I have Firefox/Chromium as a sole window on that workspace. It doesn’t blink at all if the space is split between say a browser and a terminal, or a browser and Thunar. Dillo browser doesn’t trigger blinking for some reason, but NetSurf does!
- Pocket display doesn’t blink at all
- I can see more color artifacts in both Firefox and Chromium, like blinking on the header of wiki.archlinux.org (sorry, don’t have a camera in the camp, will post the video later)
- In
dmesgall I can see is an occasionaldwhdmiqp-rockchip fdea0000.hdmi: Rate 241500000 missing; compute N dynamically, no error messages
EDIT: turns out it was all due to cable/adapter situation, see an update below Full system freeze when plugging in an extermal monitor - #5 by chorc