I am still getting the original error message in the latest betas of Xcode and macOS: This bundle is invalid. Apple is not currently accepting applications built with this version of the OS. (ID: 47b6630e-a15f-4ef7-90fc-8fbcc11555a4)

Actually there are a quite a bunch of more specific URLs, although undocumented. You can find a list of the ones discovered so far here. You want to use NSWorkspace.shared.open(URL(string: "x-apple.systempreferences:com.apple.preferences.extensions")!) // or NSWorkspace.shared.open(URL(string: "x-apple.systempreferences:com.apple.preferences.extensions?Share")!) Unfortunately there is no URL publicly known that goes to the page required for finder sync extensions, although Keka has a button to open that page.