I'm working on Slint. It is a declarative UI language that compiles to native code, the application logic can be written in Rust, C++, TS or Python, and it is cross platform, including mobile. Has accessibility through AccessKit. A live preview, so iterating on the UI doesn't mean recompiling Rust.

Compared to Electron, there is no browser, so binaries are a much smaller, use less memory, startup is fast. And the attack surface is also much smaller (no XSS)

Cross platform is not an actual achievable goal if you wish to have a pleasant UX. One size does not, in fact, fit all.