I'm pretty excited to see where the new .NET MAUI [1] goes. It's still in development, but it seems like it could be a great contender for fully cross-platform native UIs.
Paired with F# the proposed Elm-like model-view-update style would be the dream.
In addition, we are enabling developers to write fluent C# UI and implement the increasingly popular Model-View-Update (MVU) pattern.
Ah, some SwiftUI envy.