Thanks a lot for your feedback π
I would expect that a regular usb-c hub should work. I still have only iOS devices with a lightning interface so I can not recommend a specific model, but there are plenty of users with iPad Pros on this board. Maybe one of them can chime in.
Another way to do it is to use a bluetooth MIDI interface. I have the CME Widi Master and that works without any issues. Then the usb-c socket would be free for your audio adapter.