nostr:npub1cmgqvz7xr07euwkum3mjghjqcu4d3k2fcyf6g4uwwe5ggnd6fetq0wrzd2 Maybe these will help you, I think I got thing right since https://federationtester.matrix.org/ approves.
I wanted (at)marko:kaartinen.social and it already runs mastodon so I installed matrix.kaartinen.social as my matrix.
Here is a gist since I have only 500chars here đŸ˜† need to edit that someday…
https://gist.github.com/MarkoKaartinen/e7de1979963e4e0246c50672d513bfe0