What’s the best resource to learn Swift? Should I grab a Bluetooth keyboard and go through Swift Playgrounds on iPad? Or is that more for children brand new to programming?
Paul Hudson's books and guides are very good. I churned through his "100 days of SwiftUI" a couple months ago, really liked it. https://www.hackingwithswift.com
Xcode Playgrounds (different from the iPad/macOS Playgrounds app) are really helpful for learning the language or testing things out.
For a complete course, see http://web.stanford.edu/class/cs193p/cgi-bin/drupal/.
Apple also has a series on creating iOS apps. It may be too beginner focused though. https://books.apple.com/book/id1118575552