What would you guys say is the best cross-platform desktop UI framework.
My requirements:
WYSIWYG drag and drop designer
Works on Windows, Mac, and Linux
No HTML/css (I hate html/css)

Thank you
For basic things: Winforms with mono on Linux/Mac. Otherwise Avalonia or Uno.
“No HTML/css (I hate html/css)” me too.

Avalonia is likely the most mature that meets your requirements. It also has pretty solid support in VS and even the newest version of Rider.
I would say Uno seems a bit more mature than Avalonia but Avalonia has been around longer.

A framework that meets all of your criteria doesn’t exist.
Xamarin Forms can’t target Mac or Linux yet, but only sort of. Mac support is in preview, Linux doesn’t exist. It won’t be until MAUI (Xamarin Forms 6) when it will be out of preview, and even then Linux isn’t promised. You could probably set up a project structure that lets you write most of your logic in a library then use a Xamarin.Mac and whatever UI framework frontend, but that won’t be shared UI components.

Avalonia and Uno can target those three desktop platforms and use XAML variants, but don’t have a WYSIWYG designer. (Though someone below claims Avalonia has a designer, perhaps it’s in VS for Windows. I only use VS for Mac and VS Code!)
Everything else uses HTML and CSS.
Avalonia has a designer
Didn’t realize that. I’ll take a look at those 2 you recomened.
Huh, how long has Xamarin.Mac been a thing?
https://github.com/qmlnet/qmlnet
Doesn’t QT cost money?

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