Hello World in GTK[0] and Qt[1] is simpler than the OP's experience.
Gnome includes Gnome Builder[2] in most distributions, which makes it incredibly easy to start making Gnome/GTK apps. Developers can also leverage Flatpak and Flathub for near-universal distribution.
You copy paste a ten lines gtk or qt hello world, install a few packages (certainly not 20 GB), in a terminal go in the right dir, and type something like 'make'.
The mac is trying it‘s best to catch up. Should you build your app with AppKit, SwiftUI or UIKit+Catalyst "Optimized for macOS"? I can‘t tell you.
Thankfully It‘s still a relatively straightforward process to create and compile an app with Xcode, which is the only option anyway. It‘s also a 30 GB download, but at least it‘s free.
Apple is pretty clearly gearing Catalyst as a vehicle for existing iOS devs to get their stuff running on macOS quickly. The canonical way to make a Mac app is still AppKit, or if your use case is simple enough SwiftUI (which is still AppKit under the hood). AppKit is still maintained and isn’t going anywhere any time soon.
The question mostly arises when you want to build a greenfield cross platform app. I chose SwiftUI, but feel like I might regret not going Catalyst.
I think Apple doesn't usually blunder around like Microsoft with these things, but actually pulls through long term strategies. We are in an awkward transition imho. AppKit/UIKit are super mature technologies, SwiftUI is the future but kinda lacking and Catalyst is either a shortcut to speed up Mac/iOS convergence or a backwards attempt to get more advanced iPad apps. It's all fine as long as SwiftUI is actually the future. If any of the others are relevant in 10 years, more than Obj-C is now vs Swift, I'll be disappointed.
I don't believe SwiftUI is technically 100% AppKit under the hood, but effectively is, for now.
- WPF with NET 6
- Electron
- WinUI
- Flutter
- That GUI programming is complicated