One option would be using C# + AppKit on Mac and then WinUI on Windows, while sharing the view model and model layers between platforms with something like Mvvm

One option would be using C# + AppKit on Mac and then WinUI on Windows, while sharing the view model and model layers between platforms with something like MvvmCross. Here's my attempt from 2021: https://github.com/QotoQot/Octospace https://github.com/QotoQot/Octospace