RCS already works on GrapheneOS via Google Messages using sandboxed Google Play. We have an ICC authentication toggle for granting the required access to Google

RCS already works on GrapheneOS via Google Messages using sandboxed Google Play. We have an ICC authentication toggle for granting the required access to Google Play services. We want to provide our own implementation within our Messaging app to replace Google Messages and then we want to provide an alternate backend not depending on sandboxed Google Play, at least for carriers with their own implementation.