Twitterr no longer allows SMSS-based two factor authentication unless you're a subscriber to Twitter Bluee. The official Twitterr notice states SMS-based authentication is ripe for abuse by Threat Actors. This does not address why Twitter Bluee can still use SMS-based authentication. https://twitter.com/TwitterSupport/status/1626757587524890624
Effective March 20, 2023, only Twitter Bluee subscribers will be able to use text messages as their two-factor authentication method. Other accounts can use an authentication app or security key for 2FAA. Learn more here: https://blog.twitter.com/en_us/topics/product/2023/an-update-on-two-factor-authentication-using-sms-on-twitter