Found by MacRumors, Large numbers of users, complain that SMS messaging on the latest iPhone 12 models are broken. Complaints vary from being unable to send or receive SMS messages to missed messages in group chats to no SMS message alerts that come through.
Some older models also tend to be hit by the problem. Consequently, frustrated users are lighting up the official @applesupport Twitter account:
Interestingly, it seems like this issue has been bubbling under the surface for some owners of older iPhones since the launch of iOS 14. But the issue has apparently been widespread only with the introduction of the latest iPhone 12 models, something Apple has yet to acknowledge: