Well I couldn't get it figured out...ended up running the modx into a usb mixer and the usb out into the camera kit adapter...Works well...would have been cool to run it via the modx but I couldn't get the camera to receive the audio...

I'm not doing any iPhone live streaming but wanted to test out such a setup. I could get the MODX USB audio through the USB/Lightning adapter to voice memos but couldn't get it to work with the internal iPhone camera (6S plus). I found a 4 year old question about the setup on apple.stackexchange.com. The secret seems to be launch the camera app first, select video, and THEN plug in the USB interface with the MODX connected to it. The sequence of the setup seems to be the important thing. This worked for me, although I couldn't hear the audio through the phone as it was being recorded, only when I played the video back. Probably a setting I missed somewhere. Anyway it does seem to work with some limitations.

The same thread mentioned it doesn't always work consistently for all users.

In general, the reports say that this approach requires the device to present audio on the 1st 2 channels you want to record. Which apparently would be Main L/R if this worked for you - so it appears MODX works for this requirement. There's not a way to see what's going on - so it's fairly luck-of-the-draw using the built-in camera app approach.

There wasn't any mention of an alternative.