UICloudSharingController is broken and needs Apple's attention

The problem

When the UICloudSharingController is invoked on an existing share with participants, the controller should be showing the row/button to "Add people" but it doesn't.

This problem is (still) present in iOS 15.1 beta 3 released Oct 6th 2021. The problem first manifested in one of the early betas of iOS 15.0 (possibly beta4).

I have previously filed this as FB9648211 and I am getting desperate because “Recent similar reports:“ is always “None”, and this thing never gets on the Known issues list on the iOS/iPadOS beta Release Notes.

What this means

This means that you can only invite 1 person to a CKShare (even though the theoretical max is 100) until Apple fixes this. The problem affects any app that uses this controller, even those that have been in the App Store for a long time.

Side info

Apple's Notes also use UICloudSharingController but it is customized beyond capabilities of the public API, and that one does show "Add People", while the “public API” one does not. So just checking this controller within "Notes" is not indicative of the problem.

To test and verify

To test and verify, you can use any app that uses UICloudSharingController that is not produced by Apple. You can even use Apple's sample code from github: https://github.com/apple/cloudkit-sample-sharing

Steps:

1. Share a record with someone (makes them a participant with the role “user“, does not matter if they accept the invite or not)
2. After UICloudSharingController dismisses, share that record again. You will see the controller show with the title "People", it will list you as the Owner if the first row, then the original invitee, but no “Add people“ button below them

This screenshot shows the UICloudSharingController not displaying the "Add people" button below the list of share participants: