People can already install the messaging apps of their choice on GrapheneOS. It would go against our approach to choose specific messaging apps and protocols to bundle with the OS beyond SMS/MMS/RCS. We shouldn't be the ones choosing Signal vs. SimpleX vs. Element or other options but rather that's up to users to decide. We need a messaging app to handle carrier-based messaging in the OS including providing end-to-end encryption for it and the rest is up to other open source developers.