In that case, I agree with the others and say leave this up to the router - not only is it far more easier to set up, it gives you/your kid the freedom to switch between distros/OSes, and you can even swap computers without worrying about having up the controls all over again.
A friend of mine was in the same situation as you (he's also a Linux nerd), and he ended up with the router thing, and after extensive research, he decided to get a Synology router as it had all the features he was after (mainly limiting access times, monitoring and reporting). See: https://www.synology.com/en-global/srm/feature/device_content_control
And for extra filtering, you could also set the upstream DNS on the router to a filtering service such as Cloudflare for Families, AdGuard DNS Family etc.
Those of you reading this might also be interested in two_percent, which is a fork of
skim
, which in turn is a Rust implementation of fzf. two_percent is faster, more efficient and uses less memory thanfzf
, which is especially noticeable with large inputs.