Tied to a phone (as opposed to some security-specific device like a Yubikey) is a terrible idea.
It ties your authentication to something that is often lost or damages, but more importantly, something that is controlled by a third party (apple or google) and requires an expensive monthly subscription to yet another third party (your cellphone company).
TOTP is not tied to a device which is why it's a beautiful solution. You can store it where you wish under the controls you wish and back it up as you wish. You are fully in control, dependent on nobody.
Tied to a phone (as opposed to some security-specific device like a Yubikey) is a terrible idea.
It ties your authentication to something that is often lost or damages, but more importantly, something that is controlled by a third party (apple or google) and requires an expensive monthly subscription to yet another third party (your cellphone company).
TOTP is not tied to a device which is why it's a beautiful solution. You can store it where you wish under the controls you wish and back it up as you wish. You are fully in control, dependent on nobody.