Update on .NET Core 3.0 and .NET Framework 4.8
https://blogs.msdn.microsoft.com/dotnet/2018/10/04/update-on-net-core-3-0-and-net-framework-4-8/

My personal opinion is that having a cross-platform UI stack for .NET
would be a very valuable addition, but it’s a lot of work.
I am, however, not a fan of the idea to make WinForms/WPF cross-platform
because it will likely be a poor result: not compatible enough
for existing WinForms/WPF customers
while also not being a great cross-platform API (too much designed around the Windows PC).