My current solution is to use Fastmail, which only requires a phone number. I have a `username@fastmail.com` address, and used that to acquire a domain. Then, the domain is dependent on that email, is dependent on my phone number, is dependent on my legal identity.
This is, realistically not an issue, since I was going to use Fastmail anyways. Still, I'd love to skip this step and NOT require an initial email under someone else's domain.