https://developer.apple.com/documentation/sign_in_with_apple... is more “direct” than most of the documentation I’ve seen on how to implement “OAuth” with other providers. (Trying to figure out how to integrate with “Microsoft 365” is particularly painful...)

Eventually you might realize it’s based on an open standard https://openid.net/2019/09/30/apple-successfully-implements-... and that it’s relatively similar to other such standards, except with the option to mask your email, etc.

As an geeky end user, the only way I trust these services for login is if I can link more than one, or even more than one email from the same provider. That way I know I’ll have a backup in case I lose access to the social network or email address that I signed in with... it’s annoying when I can’t add a password or set an email just because I also want to login without a password sometimes...