The 2018 iPad Pro doesn't play nice with the Apogee ONE for Mac and iOS. Apogee's own USB-C cable does nothing. Using a USB-A cable with the USB-C adapter gives you audio out but nothing shows in Maestro which means no control over phantom power, internal vs. external mic, and no low-latency mixing. Apogee says the problem is that with the switch to USB-C, the audio protocols have changed and they need to write new drivers. No timeline on update though.
I suspect that this is true for Duet and Quartet as well but I don't have those to test.
I suspect that this is true for Duet and Quartet as well but I don't have those to test.