Ok,
So, enabled the 2 factor (not 2 step) authentication and opted for the text message notification option. All seemed to go fine.
A few minutes later I got an email confirming that 2 factor authentication had recently been set up, but the email address that the mail came to is in no way attached to the phone that I set the authentication up on.
That is, that iPhone has never seen the address that the email came to - not for the Apple ID, not for the email on the phone, not for iCloud - nothing.
I can't figure out what the nexus is.
So, enabled the 2 factor (not 2 step) authentication and opted for the text message notification option. All seemed to go fine.
A few minutes later I got an email confirming that 2 factor authentication had recently been set up, but the email address that the mail came to is in no way attached to the phone that I set the authentication up on.
That is, that iPhone has never seen the address that the email came to - not for the Apple ID, not for the email on the phone, not for iCloud - nothing.
I can't figure out what the nexus is.