Every cellular device, and line will support the latest GSMA version of RCS. This means RCS on iPhones will be encrypted. Those using Android will use Googles flavor of RCS through their Messages app. PCS1 feels that everyone should have a reliable data IM service, and RCS is that bridge for Android-Android and Android-iPhone communications.
For those using Graphene OS, KaiOS, and basic phones do not support RCS. These devices will instead be limited to SMS.