I recently added an external monitor to my Debian 12 laptop, setting it as the primary display while using the laptop’s monitor as secondary. However, I’m experiencing an issue where the external monitor randomly goes black, while the laptop screen continues to display normally. Moving the mouse brings the external monitor back to life. Interestingly, this happens while YouTube is running, with the audio playing uninterrupted. So far, I haven’t noticed this behavior with any other applications.
Update: I was running YouTube from within the Firefox browser, not a YouTube app (If one even exists)
This sounds like a power saving activity, which might not be caused by the OS, check your BIOS too.
I did not have this issue when only using the laptop’s display, and in fact the laptop display does not blank.
The power saving might be the port powering down, not the display.