This is interesting, but is it interoperable? Where is the code?
It is interoperable. Keychat relay only add collecting bitcoin ecash function. If the relay operator provides free service, current relays e.g., Damus relay can be used as Keychat relay. The android apk will be released first, then the code.
> The android apk will be released first, then the code. This sounds suspicious tbh. Why do this?
Agreed, there is no reason to do this. Not necessarily malicious, sometimes people just have bad ideas and/or justify them with bad reasoning. OP, please release the source code as soon as possible; no one cares if it's ugly or half-broken or whatever. When the app is released I might test it out briefly, but for something as important as encrypted comms I won't consider using it regularly until source is available (and ideally it has reproducible builds too).
Keychat message is also kind 4 event. So Keychat can use all relays which supports kind 4. The difference between Keychat messages and DM messages is encryption/decryption methods, which processed in client. Relays don’t care about encryption.