This Power Functions-style stick adapter for the Powered Up Controller, is intended for use with RC vehicles, not trains.
My fingers are too big for the little recessed buttons, and levers "just feel right" when controlling tracked vehicles or the App-Controlled Batmobile, when using a normal controller, rather than the device App. Two controllers were set up with this adapter for a recent 2-day event. They held up pefectly to the use and abuse of atleast a couple of hundred attendees.
Note: there is no access to the STOP buttons, which for RC vehicles isn't important.