Under macOS 27 using Mac Catalyst for a UIKit-based app, If you present a view controller with a table view as a form sheet or page sheet, row reordering fails to function. You can drag a row as expected but the blue movement bar never appears and if you drop the row it simply returns to its original location.
The exact same view controller presented as a popover works just fine. The exact same view controller not presented as a modal (such as the app's root controller) works just fine.
This is a serious bug affecting existing applications and being reported by paying customers.
This has been reported as FB25038883 which includes a simple sample app demonstrating the issue.