Is there a Mail API that will allow you iterate through all the email stored on a user's computer?

I’m trying to use CloudKit with my SwiftUI app. Are there any good tutorials or example projects showing how to do this? I’ve only been able to find UIKit examples.

I recently purchased an M1 MacBook Pro. I've been working on one of my apps in Xcode. I created an archive of the app and exported it using the Development option. I then connected my iPhone to the MacBook and see it in the Devices and Simulator window. When I drag and drop the .ipa file, it shows up in the list in the Xcode window, but never appears on my iPhone. I am able to run the app in Debug mode from Xcode, so I know that the app can run on this iPhone. What am I doing wrong? Or is this a problem with M1 Macs?

I've learned how to make iPhone and iPad apps over the summer. I have a few ideas for apps that I'd like to implement on the Mac. Some are only really useful on a Mac. I'm wondering if it is worth the effort of learning AppKit for these macOS only apps or can I do everything just using UIKit and Catalyst?