Hopefully this post might help others.

For a while we've struggled to put internet boundaries in place for our children. Working in technology, I have a good idea about the art of the possible, but still it was difficult. I configured the router to use a family safe DNS and used the feature on my Fritz to limit device time. Alongside using Apple and Microsoft screen time limits. One way or another the youngest child navigated the time limits leading to pointed discussions and fall outs!

I recently bought from the US a device called firewalla that has helped me win this battle. This is essentially a firewall that allows devices to be whitelisted, grouped and restricted across adult websites, games, time etc. It has also allowed me to reign in the many IoT devices that were interestingly sending nuggets of data back to China! The interface is through a user friendly Apple / Android app which can be used remotely. I have no affiliation with the company, just a very satisfied user:

https://firewalla.com/

I bought the purple version which is designed to sit in a chain between a modem and the routing of traffic across devices. However I am currently using it in the mode of the cheaper versions where it intercepts traffic (essentially using a man in the middle pattern) and enforces the rules. I'm sure there are DIY routes to achieving the same end using pfSense etc, but this device does it all without resorting to command line config!

There seems to be no UK distributor for these devices and, ordering from the US, I pondered a good while because of the potential import tax. As it happens, the device shipped from China and I wasn't hit with these charges - your mileage may vary!