> All that instead of making WPF crossplatform.

Avalonia (https://avaloniaui.net/) and Uno (https://platform.uno/) are cross platform UI frameworks for .NET.

Both work in the browser with WebAssembly. Avalonia renders to canvas. Uno can render to canvas or the DOM. Here are a couple of Avalonia demos:

https://solitaire.xaml.live/

https://bandysc.github.io/AvaloniaVisualBasic6/