Big +1 for Forgejo, also they are actively working on implementing Federation, i.e. in the future Forgejo servers will be able to exchange information as a federated network, just like good old Lemmy 😊
If you want to try the toolchain (Forgejo+Woodpecker CI), it's what Codeberg.org (run by the German nonprofit organization of the same name) offers freely.
This will allow you to browse & contribute to projects hosted on other instances without having an account there. Imagine using the GitHub search to find a project on Gitlab, then opening an issue there without ever even leaving GitHub.
The protocol is called ForgeFed.
The actions are amazing, and I was also able to integrate them with tailscale so I can build and deploy everything within my network automatically.
I run it in a vps with 1cpu and 2gb ram along several other services.