I run my own Gitea instance at https://git.benetou.fr/ but I admit didn't look much at the federated aspect, yet.

Sadly I just checked https://forum.gitea.com/c/federation/10 and despite few attempts, e.g. https://nlnet.nl/project/Gitea/ and eventually potentially upstreaming via forgejo https://forgejo.org/2023-01-10-answering-forgejo-federation-questions/#will-gitea-also-gain-federation that does not seem to be usable right now.

I'm checking https://forgefed.org/ which I learned about via checking federation on Gitea and it looks nice, in theory, but until I see an actual list of instances federated together I'll just applaud the effort from afar.