Timers are key. I have a special needs kid, and timers are doubly needed. For now I just say "20m" set the kitchen timer and when it rings, all the kids have to e.g. come to dinner.
I wish there were some good method for kids to "earn" screen time (ie, parent could add/approve) that would be automatically deducted on usage of the device(s) (with blackout times where usage isn't possible).
For iOS devices, Screen Time does that. My kids have iPads and I set certain hours they are allowed to be used at all, time limits per day, and if they run out of time they can ask for more and I can approve via my watch/phone. I set the daily time limit pretty low and then give them opportunities to earn a bit more, which I dynamically add to their total.
I wish there were some good method for kids to "earn" screen time (ie, parent could add/approve) that would be automatically deducted on usage of the device(s) (with blackout times where usage isn't possible).