All the various windows UI frameworks are stable, but not supported and not receiving new updates.

That's the problem.

And what makes matters worse is because of all the shifts, the documentation throughout MS is in just varying states of outdated. For example, this document which recommends using UWP [1] to handle high dpi problems. But of course, UWP (which was the right way to do gui in Win 10) is now defunct for win ui.

[1] https://learn.microsoft.com/en-us/windows/win32/hidpi/high-d...

WPF is also stable. Microsoft's UI strategy is similar to keeping all of Motif, GTK2, Qt5 alive while engineering new stuff into Qt6 without deprecating anything.

Btw Linux UI is not by any measure stable. It is the furthest thing from stable.