The brightness of the divice go to zero if not contreolled when unpluged. I think this bug have something to do with using the “never” settings for both “Lock Screen and Sleep” and “Turn off the screen”. I’m not sure the bug happen after reboot of not. It behave as a “Always” instead of a never.
I got around the bug with plugging the pinephone and setting both settings to 5min and a reboot.