Interesting - If you're after cross platform Flutter/Dart seems a more cross platform solution (mobile, desktop and web), or Delphi/Lazarus without the web.
There are bridges to Rust:
https://pub.dev/packages/flutter_rust_bridge
https://github.com/qt/qtbridge-rust
And this project, Relm4, is one of m.
I had to click a little to confirm that Relm4 (like the original Relm) is --as the name shows-- borrows from https://elm-lang.org
Elm comes with some really cool concepts known as The Elm Architecture (TEA) and many projects have since borrowed from it. Usually people in the FP-enthousiasts group are more inclined to like TEA. I'm not sure to what extend the brides mentioned above allow for a TEA-like architecture.
I was okay with using C as the logic layer and Lazarus as the GUI. No reason you can't do that with Rust, but it will limit the amount of spaghetti-ish patterns that you may want to create.
it's a lot of fun working at a codebase that does essentially does not allow for runtime programming errors (validation errors are still there, or API/3rd-party errors still need to pass through your code; your Elm code is essentially incapable of creating any runtime programming errors of it's own).
GUIs are hard, regardless of tech stack.
I used Qt, Gtk, React, Elm, JS-spagetti-with-some-jQuery-on-top...
And now I understand why people like Elm.
Thanks. Maybe I'll give it a bash on my next project.