I was going to try your suggestions, but I found a version of XCode on the Apple Developer site that was Beta, and reading the synopsis I noticed that it was the version that had the compatible SDKs, so for me, it was resolved by downloading the Beta version of XCode and using that. The Beta version co-exists with the prior release version in the Applications folder on the Mac.

From what I've seen from the various answers online, including StackOverflow and the Apple Forums... the App Store situation with your released has nothing to do with the iCloud container visibility issues. Various people have wondered and I've seen it emphatically ruled out as the cause in at least a few cases by people who sounded like they knew what they were talking about (in context).

mswlogo appears correct about all of this. mswlogo's very specific examples helped me verify everything What I think was not working in my case that the folder I created to to ensure the container had content in it did not match the name I I set the NSUbiquitousContainerName property in Info.plist to. After correcting that the folder appeared on my iCloud drive, finally. Took me 3-4 hours from knowing nothing to getting it working. Hopefully this helps someone else.