Using your own domain that you control for emails also comes with the advantage of easily moving providers, should there be any issues.

Hopefully, domain registrars are less prone to locking people out compared to Apple, given cause of the lockout is caused by Apple itself.

Reminds me of the time Namecheap stopped doing business with Russian accounts, even then they still gave some time for them to transfer their domains.

Only if you are not locked out of the registrar. Then your only hope is what nobody would squat your domain when it lapses.

Eg: Dynadot decided what my birthdate is a secure pin two years ago. No combination of it works and I'm not even sure if I'm not shadowbanned for the attempts.