I’m not sure if it’s just me or if it’s a problem with the latest Firefox. It doesn’t seem to be reporting to DPMS to stop the monitor from going blank.
If you also have this problem, the super + alt + B switch may be useful to toggle on/off monitor blanking.
Are you having this issue always or when for example you are playing a video?
Monitor blanking in 10 minutes of inactivity is ok when I go away to make coffee or dinner.
But it is not ok when I watch some streams on YT.
This only happens to me in Firefox after the last update.
tested with powerkit (aur). Firefox is indeed inhabiting the screensaver when playing audio/video