None of which is used by for example the Office team, which maintains their own UI Framework just for Office.

Which itself is not used by Teams, which uses electron/WebView2, even though Teams is part of Office.

And let’s not forget about MAUI, which has its own components and UI library, which as far as I know is not used by anyone at Microsoft.

And I’ve heard from people at Microsoft that the future story of .NET UI framework is “Blazor WASM”. Is that considered native? Probably not. But I’d argue it should be considered “first party”.

Let’s be honest, Microsoft’s UI framework landscape is a mess.