Codeberg or a selfhosted Forgejo would be my recommendation.

Moving repos is easy, but expect some sweat while moving actions and integrations. Also do backups.

Kinda difficult to do it in a way that isn't easy tbh!

Just locally rename your old origin to old-github or something, add your new origin (codeberg is a good shout) and then push. Maybe put a notice & link on your old repo's readme and then archive the repo on GitHub

Job done in less than 5 mins per repo

Codeberg is good and will be even better if we donate regularly.

Yes, Cideberg will do. And probaably mirroring code into Codeberg is good enough

I switched from github to forgejo and that was really easy, they have an migrate button.

If you used Github as a simple remote repository and nothing around (CI, issues, ...), you can also setup a simple bare git repository on a server to use a your remote and a backup. There is nothing special to do once you can log with SSH into the server.

I very recently did that for my personal projects.