Apple confirmed iOS 18 will support RCS messaging on iPhone and then brought RCS functionality to the first iOS 18 betas. You can text your Android contacts via RCS right now, assuming your carrier supports it.
However, Apple said that the iPhone will support the GSMA’s RCS standard, not Google’s implementation. Therefore, RCS on iPhone will lack the end-to-end encryption that iMessage gets, even though Google built encryption into its RCS system. It was clear back then that end-to-end encryption would not come to RCS on iPhone until the GSMA updated its RCS standard.
Fast-forward to late July, and a Google Messages leak reveals that encryption might be in the works for the RCS universal profile, which the GSMA supports. If that’s the case, RCS on the iPhone might also support end-to-end encryption in the near future.
According to Android Authority, the Google Messages app on a Samsung phone contains the following line of text: “+g.gsma.rcs.mls.mls-version.”