I'm starting a project with a strong need of build the UI in multiple targets (iOS, Android mainly).

I try first with html and the native webview. With iOS is totally fine, but Android is SUPER slow. I never imagine that android was this bad, but at least, it force me to do native :)

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I think that is possible to do what you describe, and I'm working something like. The key is decouple some task (kinda separate "back-end" UI from "front-end" UI):

We can do "partial" cross-platform UI, if we think that some stuff can actually cross cleanly:

- Layout (the big one, IMHO) with something like https://yogalayout.com

- The ELM architecture (https://www.elm-tutorial.org/en/02-elm-arch/01-introduction....) because a big chunk of the logic is totally cross-platform and "only" need to adapt the render of controls.

- Dispatching, events and similar stuff, that is not visual.

Then finally, the rest can be fully native:

- Controls

- Drawing

- Animations

- Call to native libs

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The big question is what to use for coding this. I'm using .net but wish to have something more low-level. I know swift and it could work for other targets (Java, .NET, native) with http://elementscompiler.com

Wish to have a coding partner to do this :)