It's currently implemented for iOS and Android, but I didn't see any mention of UWP anywhere on the related Blog Post or in the Microsoft Documentation for Material Visual
I wouldn't hold my breath, UWP is clearly dying (dead?), I don't think Xamarin team will bother adding Material for it, especially with all the bugs and missing features they need to fix on Android and iOS. You can check in GitHub issues, you will probably find out there.
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