Do you have examples of those? I'm not an expert at all on this topic, but WPF and WinForms have been released in 2006 and can still be used to develop windows graphical applications as far as I understand.

Even better as far as I can tell, WPF, WinForms, and WinUI are open source since 2018: https://www.hanselman.com/blog/AnnouncingWPFWinFormsAndWinUI...

Repositories:

- WPF: https://github.com/dotnet/wpf

- WinForms: https://github.com/dotnet/winformsblog-scottha

- WinUI: https://github.com/Microsoft/microsoft-ui-xaml

Now, I'm not familiar with those technologies, and don't use them, so I may be missing some things.