ios refuses to verify email address

Updated my iPhone 8 to ios14 and when I get to the “verify email address” screen, it wants to send a verification code to the email address I use with my Apple ID in order to turn on two-factor authentication. So I hit the send code button and when the code comes through, I type it into the phone. But then I get a warning that says:

Cannot Verify Email

This email address is not available.

Choose a different address.

And that’s it. I’m stuck. I can’t use my phone for anything and I don’t know what the **** this message means. I’ve been using this email with my Apple ID for over a decade.

Anyone else get this and know how to get around it?

This is my only phone so now I don’t have a phone until I get this fixed.