Element X actually runs really well on macOS already on Apple Silicon; I regularly use it as my desktop app whenever Element Web is having... issues. It would be amazing to plonk matrix-rust-sdk into Element Web and switch Electron for Tauri or something... but one thing at a time.
It would be nice to provide first class support for state of the art web clients (both desktop and mobile). That would fit your opening stance of "Matrix has been going for over 9 years now, providing an open standard for secure, decentralised communication for the open Web" more than apps tied to the iOS/Android app ecosystems.
I’ve wondered about this for a long time: Why not Flutter? Should give you one codebase for all platforms, while being significantly faster than webtech-based solutions.
I guess we just prefer to use the platform’s native UI (SwiftUI/UIKit, Jetpack Compose, HTML) on each respective platform, rather than an abstraction like Flutter. All the heavy lifting is done by matrix-rust-sdk now anyway.