Flare
Flare is a simplistic web browser for macOS built using UIKit. It demonstrates a custom address field toolbar item using an NSTextField subclass, bridged via AppKit, tabbed windowing, dynamic menu updates & window state restoration.
Web browsers are not an app category best served by Catalyst; with that in mind, this is provided as an illustrative piece of example code for the above. Ask me about it at https://twitter.com/stroughtonsmith.