Surprisingly, Microsoft Authenticator works very well. On iOS it lets you back up your authentication tokens to iCloud and on Android I believe there is some way to do this too (I don’t have an Android phone so idk). I would avoid Google Authenticator because to the best of my knowledge there is no way to back up, and at some point in the past it crashed on me and I lost all my 2FA logins, which was a huge pain to recover from.