Gitness, an open-source GitHub competitor which hosts their open-source code...on GitHub... with a prominent call to arms on their landing page to star their repository...on GitHub...
If you don't even use your own product why should anyone else use it?
Gitea does this too, unfortunately [0]. Codeberg (Forgejo) [1] and GitLab [2] both are dogfooding with no presence on GitHub, which is definitely a better look.
[0] https://github.com/go-gitea/gitea