@OOPer damn, this is a bummer. As a last resort I'll try to strip all the code from the old app to a bare minimum, compile and see where I'm failing. Thanks for your help

@OOPer, I've tried the whole weekend to come to a solution. Even created a new objective-c app and migrated the code needed to interact. Same code, same developer account, same account on the simulator: no data from Cloud Documents.

They're the same: Bundle identifiers, group and icloud configs. Removing deprecated code has no effect. I have an ipad with the old production code running and showing data, so I'm sure the my swift porting is incorrect somewhere. During development the development of the app I've enabled cloudkit alongside icloud documents and created another container. Then I disabled either cloudkit and the new container. This could be helpful?