Gitea can be easily self-hosted and supports Gitea Actions, which are largely compatible with GitHub Actions. I’m about to try it out. https://docs.gitea.com/next/usage/actions/overview
https://gitea.com/gitea/act -> https://gitea.com/gitea/act_runner
https://code.forgejo.org/forgejo/act -> https://code.forgejo.org/forgejo/runner