Why should I need root or build my own ROM to use an alternative app implementing the whole RCS low level stack ? I sure don't have to do this to change my SMS app (yet). It may be the modem or the OS doing the low level stuff for SMS I don't care, a proper "mobile os" would provide APIs to do it. Why doesn't the AOSP Messaging app implement it if it's so standard and open ? https://android.googlesource.com/platform/packages/apps/Mess...