I have started using Avalonia, and even though I am still learning, I am very satisfied with it. There are growing pains obviously, but as you said, I have no confidence in Microsoft UI frameworks.
Not sure about that, I suppose it depends on the targets each .NET version support. For example, .NET 8 will drop RHEL 7 and only RHEL 8 and later.
And to play devil's advocate: this won't work for all existing .NET applications. If you use reflection (which is AOT unfriendly), chances are that you will have to rework a ton of stuff in order to get to a point where NativeAOT works. There's a middle solution though, called ReadyToRun, which has some advantages compared to running fully with the JIT compiler.
I have started using Avalonia, and even though I am still learning, I am very satisfied with it. There are growing pains obviously, but as you said, I have no confidence in Microsoft UI frameworks.