Gitea is nice, open source and self-hostable (especially if you already have a VPS for your project). It's also possible to mirror or backup Github/Gitlab repos. AFAIK Gitea is working on a federation feature, so you could browse all federated repos (improves discoverability) and commit with a single sign-on.

Codeberg.org is a public registration Gitea instance (also offers a similar service to Github Pages for static websites). HackLiberty.org also operates a Gitea instance.

Otherwise there is a bounty for an implementation of Git on Nostr: https://bountsr.org/nostr-based-github/ Some projects here: https://makers.bolt.fun/project/git-nostr and https://makers.bolt.fun/project/nostrya