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.
Moving goalposts, the point was what are the native APIs.
Office framework would not exist without Win32, and usually it is made available on Win32, e.g. ribbon as common control.
Xamarin was never used at Microsoft, how to expect the rewrite to go any better. This acquisition was a mess, almost everything from Xamarin is gone.
Again, not a native API.
Blazor only matters for Web applications and PWAs, unless Windows turns into ChromeOS there is nothing native about it.
Blazor is only for web applications, until you run into Blazor Hybrid, which doesn’t produce web applications!
That is marketing gimmicks trying to get additional market share, and the current adoption failure of MAUI customers, as teams leave Xamarin ecosystem after the Xamarin.Forms to MAUI (incompatible) rewrite.
I give zero value to Blazor Hybrid, from my point of view it doesn't exist.