Issue: Blocking YouTube on the firewall is blocking Google Docs and Hangouts
Context: I followed the instructions here to configure firewall reject rules for YouTube, Discord, and Twitch because my kids are doing remote school full time using Chromebooks. The problem is they are distracted by Chrome tabs open to the sites mentioned. The rule works fine blocking Twitch and Discord but YouTube is blocking more than YT.
also for other websites/apps you can ssh to your openwrt router, type tcpdump -ni br0 dst port 53 | tee log
and pop open a browser only connecting to youtube. Only have one LAN/WLAN client online when you do this. The file 'log' will contain all outgoing dns requests from interface br0, in cleartext. That could work as a base for a blacklist, but you have to trim it, and be careful to remove stuff like 'update.windows.com' and similar domains.