That's right, Signal (https://kerkour.com/signal-app-rust), Proton (https://kerkour.com/proton-apps-rust), Matrix, Wire and many more are using a share, cross-platform Rust core and a platform-dependent UI layer.

But it's not only the security-critical paths, but also most of the business logic (see the 2 posts above).

I agree with everything you say. But wow, does that comment sound like AI. Probably Grok?

Not saying you are AI, you might just be a heavy user who picked up the same patterns