Carriers are only slowly adapting to iOS 18 beta RCS integration

https://9to5mac.com/2024/06/24/ios-18-rcs-iphone-beta/
No signs of RCS were seen in the first beta of iOS 18 released earlier this
month. However, the second beta of iOS 18 released on Monday added a new
RCS toggle in the Settings app, at least for some users. This has made beta
testers wonder why some of them aren't seeing the toggle, or even why the
feature isn't working despite the toggle being turned on.
Well, we now have the answer.
As seen by 9to5Mac in the iOS 18 beta 2 code, RCS support on the iPhone
relies on Apple working with carrier partners to get them to update their
bundles shipped with iOS. Right now, only a few carriers (such as AT&T and
T-Mobile in the US) have updated their carrier bundles to support RCS on
the iPhone.
Of course, there's still time for more carriers to work on enabling RCS
support on the iPhone by September, when iOS 18 will be available to the
public. But at the same time, this means that most beta users probably
won't be able to test the new feature.