I find that rules and firewalls and schedules and blocking are a fools errand - it is a cat-and-mouse game that you can't win.
So we just turn off the Internet.
We have a different wifi network for the children that has a very restrictive schedule. Basically just Fri/Sat night and 15 mins on weekday evenings to send messages to friends and check school assignments.
The 7 year old gets his Nintendo Switch on Saturday and Sunday mornings. The older two have their ipods/iphones and can use them anytime they want. They are just offline.
The reason this works so well is that we live in a place that has zero cellular signal. If they need to do homework, they plug into an Ethernet switch and sit at the dining room table with a laptop.
The other reason this works so well is that our children are not our friends. We don't have a peer relationship with them and we don't owe them explanations as to why our family is different from other families or blah blah blah.
Complaining is expensive and they know not to waste that energy.