Hi freebsd-net!
After a lot of google and tinkering I have hit a brick wall trying to set-up my new ISP which uses PPPoE. I'm at the point where IPv4 works fine 100% for all websites. But from the moment I turn on IPv6 all sites that prefer IPv6 stop working, I have confirmed that routing table etc all look good. So I'm more suspicious to a MTU / MSS issue. Although I cant find that much info about it. I have tcpmss fix turned on in my mpd.conf There seems to be a few sites like google.com and youtube.com that keep working. I have googled thoroughly but I was unable to find a fix for my problem. The one close to my issue seems this issue from 2020:
