USB audio to ipad: how to monitor?

I have no problems to connect the opz to my usbc ipad prointo AUM, it shows up as a hardware input and output device. But how can I monitor this now? I have a hub with 3,5mm connector, but if I plug my headphones in, the opz disappeares. If I plug it into the opz, all I hear is the opz, although AUM sends to the opz. Is there a way to switch off direct monitoting in the opz?

That would be the killer feature to integrate the opz into an IOS setup!

highly anticipated! that would make sense.

I added a post to the suggestion thread about this. It would be such an awesome (and seemingly simple?) feature.