Microsoft recently announced that it is returning to the idea of creating controllers for smartphones. The company had already been developing gempads four years ago, but then it was decided to freeze the project. Perhaps the return to the controllers is associated with the imminent launch of its own streaming service, which will not be completely comfortable to use on touch screen devices.
At the moment, the company's designers are testing plug-in modules, like the Nintendo Switch console. Devices printed on a 3D printer are tested for usability.