On the other hand, Xamarin.Forms had an announcement recently, an announcement that Hacker News missed. I submitted the news a few days ago but it didn't reach the first page:
https://news.ycombinator.com/item?id=14383467 ->
https://blog.xamarin.com/glimpse-future-xamarin-forms-3-0/
TL;DR:
Xamarin.Forms will support desktop environments:
- Windows (WPF)
- MacOS (Cocoa)
- Linux (GTK#)
This is on top of the mobile bits: iOS, Android, UWP.
As an added bonus, they've added Xamarin.Forms embedding into native interfaces.
It's actually major news since Xamarin.Forms would become the first cross platform UI toolkit that:
1. supports both desktop and mobiles
2. is backed by a major vendor
3. is truly usable from a memory managed language as part of the core offering