If you have not switched from two-factor authentication via SMS on your Twitter account before today, March 20th, your account will have two-factor authentication deactivated. From now on, only accounts subscribed to Twitter Blue will have access to the security feature.
It is still possible to use two-factor authentication via an authentication app without a Twitter Blue subscription, so if you want your account to continue to be extra secure, just go to the settings on Twitter and activate it.
