Not a perfect solution, but I use NextDNS which has profiles, and can set allowed services and times of day for them, Online Games, Video Streaming etc. This is set in the phone’s DNS setting so works via WiFi or cellular.
I’ve started to use the excellent DNS Toggle on my phone to quickly enable/disable it for the really annoying sites that block ad blockers etc.
In terms of app control itself, I still use Family Link begrudgingly as well like you for Android phones. I access it via the web page which thankfully still works so I don’t have to have the Google app installed.
Not about certs, but I found the opposite moving from Caddy to Traefik: in amending the caddyfile, I had to restart the Caddy service which would kill any open connections that were being used. In Traefik, it’s dynamic, so can update the services without having to restart Traefik itself.
My main move to Traefik was due to file transfers for reverse proxy services like File Browser slowing down after a period of time, whereas in Traefik, they stayed at a constant speed.
I now run Traefik as part of Pangolin, so most config is set by that.