All roads seem to lead to Swift 5 in AppStore. Which only runs on iOS 16. My iPad Air 2 can not run 16, seems I need Swift 4, but I have been unable to find it. Thanks.
Looking for swift playgrounds for iPadOS 15
if You write in swift 4 it will be compatible with swift 5. So except if you want to use some specific swift 5 feature (as if let *** short syntax) so you can use swift 4.
Unfortunately this is a general problem with the App Store. Only if you already once downloaded an older version of Swift Playgrounds on your account you can load this version again on older devices that don't run the current version. If you try to download an App for the first time, only the newest version will be offered and users of older devices have a problem.
I would be happy to write in Swift 4 if I could… that’s the dilemma.