So, years ago when I first signed up (to register one of the old 4 character App IDs I think), my Apple developer ID was just a seven character (initials and surname) string - not an email address, no @ or anything.

Later, I signed up to, I think, iTools when it came out, with the same 7 characters before the @ sign. This eventually got converted to an @mac.com address, and then a @me.com address (though I kept using the @mac.com address, so the @mac.com and @me.com versions still work as aliases of my @icloud.com email address, which is the same 7 characters before @icloud.com).

I forget the sequence, but assuming that my developer ID (which we’ll call abcdefg) was the same as abcdefg@mac.com etc, I managed to sign up to the App Store with abcdefg as my Apple ID, and register purchases against it, and also managed to sign up abcdefg@mac.com as a completely separate Apple ID for Icloud, including email. So, I had two IDs that were essentially the same, that I didn’t want to give either up, but couldn’t merge.

Then the Apple developer program insisted on an ID that was an actual email address, so I changed abcdefg ID to my @gmail.com address (with a different string of characters before the @ sign), for use on the App Store and as my Developer ID.

I then decided it would be better not to have my Developer ID associated with either Google or Apple, so created another Apple ID with an email address at one of my own domains, and waited for my paid developer membership to expire, which was a couple of days ago. So, yesterday, I went to pay the annual membership for the new ID, discovered that I hadn’t turned on 2-factor authentication for that ID, then discovered that there was a 3-day wait on being able to request 2-factor authentication. So, I’m now waiting for Saturday morning to use my new developer ID to downloads various betas and start learning SwiftUI.