I've used UIBarButtonItem(title:image:primaryAction:menu:), with nil for primary action, and only a UIMenu for iOS / macOS and it has been working fine for iOS / iPadOS 14,15,16 and macOS 11 and 12.
Now for macOS 13 (Ventura), where the navigation bar has been moved to the title bar, the UIBarButton item is disabled and does not show the UIMenu when tapped. This is a huge problem for my apps now. If a primary action is defined, then the UIBarButtonItem is enabled, and shows a dropdown arrow to the right of the item that activates the UIMenu option.
Is this a bug with macOS 13? I've filed a report with Apple but no response yet.