Hey look, it's one of the folks I'm talking about:

I’m assuming you’re trying to turn your monitor off while there is still an active HDMI signal for some reason? Otherwise why wouldn’t you just let the monitor put itself to sleep when it detects no signal like everyone else I know?

Nah, I'm trying to let the monitors put themselves to sleep, genius. That's what's not working. There shouldn't still be an active HDMI signal. Disabling DCC/CI doesn't fix the problem, either, it just goes back to the monitors not actually ever shutting off, just turning off for a moment and then coming back on, with plasmashell crashing instead of the power monitor. I don't care at all about controlling monitor brightness with DCC/CI but when the defaults cause crashes that's an issue.

This is an out-of-the-box fresh install with no old dotfiles moved, complete refresh. These were the defaults I was given. Deciding to set your monitors to power down after 10 mins of inactivity shouldn't be causing crashes. i shouldn't have to manually turn my monitors off or do hacky shit with xscreensaver to get it working in fucking wayland just to not have monitor burn-in