Tonight I introduced a schedule in my OpnSENSE firewall, attached a blocking rule to it and added the mac addresses of some minor living in my house.
This will make sure said minor will have access to the Internet at some times and no access to the Internet at other times. Most notably no access during the late evening and night.
When I was all in the Apple ecosystem, I just used screentime settings and accepted that the system was not effective on things like a gaming console.
But this seems like a pretty nice way to prevent accidents (although the phone also has cellular, don't tell anyone)
