I'm late to the party, but Gitea as has Gitea Actions[0] based on their fork[1] of act[2]. Their claim is that it's mostly compatible with GitHub Actions. I wonder if this can be spun off to have the control plane run separately and integrate into GitHub Action. Or alternatively mirror the repo for Gitea Actions only.

[0] https://docs.gitea.com/usage/actions/overview

[1] https://gitea.com/gitea/act / https://gitea.com/gitea/act_runner

[2] http://github.com/nektos/act