Prevent screen brightness reduction while watching a video on youtube

[maycne.sonahoz]

This seems relevant.

Firefox no longer prevents monitor power saving when fullscreen is active

Yesterday I started experiencing an issue that didn’t use to happen just the day before: Firefox will sometimes not prevent the screen from powering off when running a fullscreen application, such as games or other pages that support the mode. Playing Youtube videos still seem to prevent monitor standby accordingly, but other fullscreen elements no longer do. I use Firefox 107.0 on Manjaro Linux (KDE Plasma) running on the amdgpu video module. Is this a known bug and already known or should I g…