In my quixotic quest for proper parental controls, I finally found NextDNS. You might be familiar with "family friendly" DNS services that screen out adult websites, force Google to use SafeSearch, etc. See cleanbrowsing.org
or Cloudflare's 126.96.36.199 DNS server.
NextDNS is different - it offers configurable DNS for ambitious users. It has excellent DNS-based ad blocking, just like pi-hole. It also has a large list of questionable websites that you can easily turn off. Like "no tumblr".
You can also tell it to block EVERYTHING by default, and then just turn on the websites that you want your kid to be able to access. In my house we have two different setups. One kid has everything turned on by default, with a few websites turned off. The other kid has everything turned off by default, with a few websites turned on. Incredibly helpful when getting the kid laptops sorted out for school.
Great product. New and improving rapidly. Mostly of interest to tech savvy users, I think.