My progress on the Mac bug is here
@ftrias - In one of your responses on this thread you mention "the Mac sends a SET_INTERFACE to 0" - how are you able to monitor the information which the Mac is sending? I've tried to find USB packet sniffing software for Mac but can't find anything (USB Probe doesn't do real-time logging). I'm considering buying a hardware USB protocol analyzer but would like to avoid that cost if at all possible.
Is it possible to change number of channels, available in AudioInputUSB class? I'm looking for a way to define 4+ channel USB-audio interface. New Teensy 3.6 should be fast enough to handle this, IMO.