Piano does not currently offer SMS-based authentication. Our passwordless checkout/registration approach does allow for email-based authentication.
However, if you would like to move any such SMS functionality from a 3rd party provider over to a Identity Management implementation, that should be possible. You can plug your existing login and registration forms into the Identity Management API. Once a user has completed the first part of a passwordless login, you can use the is_magic_link_sent parameter to indicate that you do not wish to send the login link via email. Instead, you can send it via SMS.
Once the user validates, you can take the token you received from that login attempt and pass it on to the front-end by setting it as the _utp cookie. For example, using the approach described here.
If you'd prefer to handle that without storing a token, after a successful SMS verification, you could instead call the token endpoint to create a new token for the user.