If I was building a cross platform native app with .NET I'd probably use Avalonia right now.
I think not supporting Linux was a tactical error, though. Some people will put up with a lot for Linux GUI support, and some of those people are the types who can resolve problems with your half-baked GUzi framework.
Support reasons. Still isn't the year of Linux Desktop.
Were I live and work (IT and consulting in central south-east Norway) it has been the year of the Linux Desktop on and off since 2009.
That was the first time I worked full time at a place that deployed Linux for everyone and everything that didn't have a verified reason for needing Windows.
I think we had one 3rd party trading software running on a Windows machine and maybe the CEO and someone in accounting got Windows.
Everyone else was upgraded to Linux and it worked beatifully. It was my job to support the sales department with desktop related issues and it was absolutely no problem to do it while also being a productive developer.
Since then I have not worked on a place that required Linux, but I think most of the places I have worked on since has had Linux as an option as long as you supported it yourself, and some places also have been very active writing how-tos and working with me to troubleshoot issues that were related to Linux, since many of them were also Linux users.
At the moment I use Mac, but at my current job I'm also allowed to use Linux.
Sure, Microsoft could pay more employees to work on it faster, but Linux loves and prefers open source from Linux devs "untainted by Microsoft", right?
Huh
Alternatively, just because you're on .NET doesn't mean you need to use Microsoft sanctioned UI toolkits, just as C++ has no "official" UI toolkit. You're free to pick up some GTK or Qt bindings if you want a native feeling and your application is already architectures correctly. Alternatively, throw Imgui at it if you just need dev tooling, or maybe try other cross platform toolkits in the ecosystem like Avalonia or Uno