Hello! This is answered in the Summary of the iPhone Duo Group Lab https://developer.apple.com/forums/thread/847644?answerId=906290022#906290022 How does tabSidebar (UIKit) or sidebarAdaptable (SwiftUI) behave on iPhone Duo? When using sidebarAdaptable and SidebarAdaptableTabViewStyle in SwiftUI, or UITabBarController.Mode.tabSidebar in UIKit, the system presents the platform's regular tab bar or an adaptable sidebar depending on the active context, orientation, and pose. In general, iOS displays a bottom tab bar rather than adapting into a sidebar the way iPadOS does. You can opt into a sidebar on the inner display of iPhone Duo by setting the default tab bar placement to sidebar in SwiftUI, or the preferred placement to sidebar in UIKit. If you are seeing a different behavior, could you please file a feedback report with a sample project that reproduces the issue, and share the FB number?