TidBITS has some coverage:
I like giving TidBITS a plug because I’ve been a reader since TidBITS started as an email newsletter for Mac users (long before iPhone and well before Apple became the tech industry behemoth it is today) and because TidBITS uses Discourse for its forums as we do.
On a side note, since it might be of some interest to Android users as well, RCS on iOS appears it will be hit or miss in terms of carrier support. Generally, it looks like it will be available on the big 3 MNOs proper, most of their flanker brands and a relative few independent MVNOs at launch on September 16, 2024. Any iPhone running iOS 17 is capable of updating to iOS 18.
@cbwahlstrom, if your son is still with UScellular (not to be confused with US Mobile), their Apple carrier bundle looks like it is RCS enabled for iOS 18.