One problem is that GH gives you no way to disable PRs. And even if you write in BIG BOLD LETTERS that PRs should be on Codeberg not GH, people get upset and make a fuss over their "ignored" PRs and it ends up making unnecessary headaches for you over and over.

Glad to see codebrg getting recognition. The age of relying on for profit corps for our digital commons needs to end.

This seems workable to me. Github rose to prominence on the back of oss. What oss giveth oss can take away.