Also encountering this; filed FB11727587 with a sample app that reproduces the crash. Has anybody come up with any temporary workarounds for this?

Also struggling with this one -- in my case, the content view is a wrapped UITableView (for better performance on a very large dataset) and I can't get the NavigationSplitView to advance. So far the only way I've gotten anything working at all is to have a "fake" List that is bound to the selected item. NavigationSplitView { List(selection: $selectedFolder) { Text("Inbox").tag("Inbox") } .navigationTitle("Folders") } content: { if selectedFolder == "Inbox" { ZStack { MessageListView(selectedMessage: $selectedMessage) // Hidden list to help with navigation List(selection: $selectedMessage) { if let message = selectedMessage { Text("\(message)").tag(message) } } .hidden() .frame(width: 0, height: 0) } } else { Text("Select a folder") } } detail: { if let selectedMessage { Text("Message \(selectedMessage)") } else { Text("Select a message") } } It kindof works, but there are rough edges.