PasteboardPublisher is a simple library that adds a Combine publisher to AppKit's NSPasteboard class.
I created this because there is currently no way to "subscribe" to changes to an NSPasteboard, so it must be done by repeatedly polling the pasteboard's changeCount. This library just abstracts that away, and adds Combine compatability. I used this library in my pasteboard filtering app, Plain Pasta, to great success.
I used many articles to build this library, but the one that finally connected the dots for me was Creating a custom Combine Publisher to extend UIKit by Antoine van der Lee.