Any TOTP where the user enrolls it on account creation, without going through a third-party service. Or SMS on a burner phone. Both are pseudonymous, since usin

Any TOTP where the user enrolls it on account creation, without going through a third-party service. Or SMS on a burner phone. Both are pseudonymous, since using the same authentication at multiple sites could be linked, but neither have to be tied to a real-world identity.