So no, Githib is not a metric for enterprise development.
And you are right Winforms is legacy, all modern Windows applications are written in WPF.
I have been doing it the last 4 years, and dispite the HN Web bubble, out there in the enterprise there are companies actually adopting UWP and migrating their laptop fleet to Windows 10.
The writing is on the wall - not even MS is falling over itself to support WPF in .Net Core.
Not everyone is using Citrix, and there are many markets, like life sciences, ticketing systems, factory management and many other domains, using non networked devices with native UIs in WPF.
Of course MS is not supporting WPF on .NET Core, they already announced XAML Standard and Xamarin.Forms is going to support Linux and macOS as well.
Also they have big UI announcement planned for BUILD as discussed on .NET Rocks interview with Scott Hunter.
Besides my stay at research institutes, I never worked on companies where IT allowed anything other than Windows as development machines.
Linux when required is only VM based or servers accessed via ssh.
Macs are only allowed on macOS/iOS related projects.
Docker remains a buzzword for the majority of customers, another box to tick besides big data and ML on slideware.