Good luck killing SMS when the RCS APIs are for Google Messages (and rebranded Android OEM messages apps) only. The few paid RCS messaging APIs that exist are priced like caviar compared to SMS.

Yeah. The reality is that RCS is happening and leaves Signal in the same position they are on iOS where SMS is only supported/allowed via Apple's app and they can't touch.

SMS-only users will be left in the cold. It used to be that if you use SMS you were a pariah on iOS with low quality MMS etc. Pretty soon SMS users will be a pariah on both iOS and Android. Not to mention how things change if/when the EU forces Apple to support RCS.

Furthermore RCS is adding encryption. So Signal users who communicate via SMS are missing out on that possibility to improve their use of encrypted communication with users who don't use Signal.

The narrative of the Signal+SMS silent upgrade is also falling apart. As RCS support continues to roll out, you are actively downgrading a user's experience if you install Signal as their SMS client.

Frankly I don't see these facts support SMS in Signal being worth any developer effort. And if literally anything in the SMS stack results is a security breach of a Signal user, Signal gets all the egg on their face. It just does not make sense for SMS to exist in Signal.

Right, just like MMS killed SMS. Good luck trying to kill simple plain text message with shaky Google RCS support, which ain't some international open standard.