With Rust I imagine taking advantage of LLVM you could just import the business logic into whatever app environment you need to and work it that way. Has anyone here tried that? I would love to hear how it went.
Check Sciter/Go : https://github.com/sciter-sdk/go-sciter
It is used precisely that way: backend - Go, UI - Sciter.
You need a protocol over TCP. Something standard and easy to use, hopefully one that people already know and has wide support from libraries. HTTP?
Native UIs are nice, but the cool kids like to stylize their UIs. Things like gradients, shadows, highlights, animations, etc. And wouldn't it be cooler if you go to all that trouble to stylize your UI to have it look the same on all platforms? What if you add another layer on top of the underlying UI framework? Something that lets you compose UI elements from basic shapes, maybe a way to separate the layout from the style? HTML + CSS.
Oh wait, we reinvented electron again.