AMD or NVidia?

Most games that I play work well on Linux with AMD. Most who have problems seem to have Nvidia. Anti-cheat stuff can be an exception though so best to ensure what you enjoy works.

If you can check hardware compatibility before hand, it helps. An up to date kernel like Fedora, OpenSuse TW or Arch can help. Wine recommends up to date kernel.

YMMV. I’ve seen issues in migration from Gitea to Codeberg. Always test first.

No one goes for source unless they have recommendation or use it and it wouldn’t matter in those cases where it is hosted.

Lot’s use Github, but it doesn’t matter. Lots hate Microsoft too.