TOTP itself doesn't require a phone number, but the Authy phone app from Twilio managed to screw up their TOTP implementation and it requires a phone number. I

TOTP itself doesn't require a phone number, but the Authy phone app from Twilio managed to screw up their TOTP implementation and it requires a phone number. I filed a bug with them and they finally acknowledged that it's deeply embedded in their implementation.