Apple has released new builds of iOS 12.1 beta to support the latest iPhe XS and XS Max, including the delayed Group FaceTime feature.
The first beta of iOS 12.1 was released earlier this week for existing iPhes, but now that the iPhe XS and XS Max are available to customers, additial builds have been released.
This comes at the perfect time for customers who like to receive new iPhes today, because it is impossible to restore a new phe from a back-up of a newer versi of iOS. So if a user's current iPhe had iOS 12.1 beta, there is no way to restore a backup of that device so that that versi of the operating system runs until the new iPhe XS or iPhe XS Max is also updated to the beta.
The iOS 12.1 beta seems to be a minor update so far, usually with support for Group FaceTime. Other minor changes were found in the code that is probably intended for the new iPads that will land this fall, such as horiztal Face ID support.