The star federation feature is now merged into forgejo and will be part of the next release version :-)
You can check out the PR that contains an overview over the new feature: https://codeberg.org/forgejo/forgejo/pulls/1680
We also wrote a 'How To' which explains how to try out this feature: https://domaindrivenarchitecture.org/posts/2024-06-05-howto-federated-stars/