I found screen is turned off even when app is in fullscreen, like watching movie or gaming.
Submitted issue here: 507199 – Don't turn off screen when any app is in fullscreen
Dev replied that the power management should be done by app not KDE.
But since many apps don’t handle this (including mpv or vlc, and games run by proton i guess?), perhaps KDE can handle this? This would make things easier.
E.g. add a new checkbos in Power Management settings page, like “Don’t turn off screen when app is fullscreen”
It’s strange that apps like mpv and vlc, and games don’t inhibit power management: they all answer to use cases where the inhibition is obviously needed. Maybe there’s some problem with your configuration?
Also, your bug report does not give any hint on the misbehaving apps; this is important because no one could reproduce the issue, given that
when playing movie or gaming, the screen is turned off after inactivity
is false: there are lot of apps I use that inhibit power management, for example browsers; therefore one needs a specification.
you can check the power mgmt item in the system tray to see which applications (if any) are preventing sleep or screen locking.
or you can also manually prevent it.