Problem statement
This article explains how to configure SMS as the default phone factor.
Solution
There is no setting to make SMS the default factor.
However, if the Auth0 tenant has the Custom Delivery Method enabled for Phone MFA and SMS and Voice selected like below:
When the first-time users select the phone factor, an option appears with “Text Message” is pre-selected by default.
And if the user has “preferred_authentication_method”: “sms” in their user profiles, the first time they log in, they will see the SMS by default like this:
