ForgeFed is an ActivityPub Extension to allow cross-forge (git server) issues, pull requests etc. without having to create an account on each server. Forgejo (a Gitea soft-fork) is actively working on this integration.

GitLab don’t have the monetary incentive to implement federation. Most of their revenue is coming from big companies which are mostly using private GitLab instance and won’t want their projects federated.

That being said, hope this changes can get merge as somebody already done the dirty work for them. The beauty of open source.