Currently Maui is Microsoft’s cross platform UI. If instead of the native ui wrapper, you want to use a html based ui, then Maui hosts Blazor via a webview. Blazor can also be a website (maximum cross platform)
the Maui UI is based on Xamarin forms which used xmal like WPF, but different controls.
In todays mobile world, Maui/xmal forms is pretty dated compared to SwiftUI and JetPack. One would hope Microsoft would develop a competitive option to replace Maui Forms.
Picking a third party option like Uno or Avalonia has the risks and benefits of third party.
note: I only do web and mobile (no desktop). I have used cross platform mobile tools in the past, but like many gave up. The build chain is always finicky, and it’s hard for the components to stay current. The power and simplicity of SwiftUI, JetPack and native build tools overrode the value of a common language and shared code base. But my apps call a website backend, so there is a lot of shared enterprise code.