[kredd]

I understand it’s a naive statement, but in order to log in into your email you would end up relying on some other sort of 2FA. And we’re back to square one to relying on SMS, because UX of other authentication flows has irrecoverable flaws.

[hedora]

Exactly. You could use a trustworthy mail provider with a domain you own (registrar and DNS provider in two other accounts, probably), and then a second mail account for the 2FA for the other three accounts, but then what's the 2FA for the second email account?