I've been working with Xamarin / Mono and having a Cocoa front-end with a C# back-end is really the best of both worlds. Everything looks native, is snappy, use

I've been working with Xamarin / Mono and having a Cocoa front-end with a C# back-end is really the best of both worlds. Everything looks native, is snappy, uses relatively little memory and all of the not so immediately visible Good Stuff for macOS like accessibility, document state and AppleScript just works out of the box. Most cross-platform solutions are awful in at least one of those three, usually all of them.