With today’s general release of iOS 18, RCS messaging on iPhone is now supported by Apple but not necessarily your provider
It appears the following have RCS on iOS support
- AT&T (including FirstNet)
- C-Spire (regional MNO)
- T-Mobile
- UScellular (regional MNO not to be confused with US Mobile)
- Verizon
Other providers using AT&T’s network:
- Cricket
- Consumer Cellular
- PureTalk (possibly including h20 Wireless, which shares ownership with PureTalk)
- RedPocket (as well as apparently sub brand FreedomPop and possibly UNREAL Mobile)
Other providers using T-Mobile’s network
- Metro by T-Mobile
Other providers using Verizon’s network
- Spectrum Mobile (Charter)
- Xfinity Mobile (Comcast)
- Visible by Verizon
- Tracfone brands with carrier settings update 59.1 (dropped separately OTA today)
The above is based upon examination of relevant carrier bundles for the iOS 18 release candidate and this Apple Support document. It’s entirely possible I’ve missed someone. If your provider offers service on more than one MNO network, only the option noted is RCS enabled at this time.