Guitar/vocals here. Just got an iPhone 13 Pro which has an excellent camera. I'd like to do live streaming with some basic audio mixing/effects ITB but I haven't yet figured out if it's possible.

What I'm trying to do:
HQ audio in, using Zoom H5 as a USB audio interface
(through Apple's Lightning to USB 3 Camera Adapter)
Basic effects/mixing through some app (EQ, reverb/delay, compression, volume/pan)
HQ video through iPhone built in cam

While the H5 successfully replaces the built-in mic when connected, I haven't yet figured out how to route the audio through a mixing app on the phone and combine it with the camera video.

I heard about AUM and Audiobus. Purchased AUM and figured out how to set up an effects chain but can't figure out how to route the processed audio with the camera feed.

Are there iOS streaming apps that will allow one to select AUM (or Audiobus or Garageband, etc) as the audio source and the camera as the video source? Or any other solution to doing it all ITB on the iPhone?

Though doing it all ITB on the iPhone would be my preference, the alternative is to do the mixing outboard so the signal through the Zoom H5 is already processed. I could either do that with my Macbook using a DAW/plugins or through an old Mackie 1402-VLZ mix board (in which case I would need a hardware reverb on the effects send; or use the Macbook/DAW as the the effects send/return, if I wanted the extra mic inputs on the Mackie).

Right now, 2 mics for starters, voice and guitar. Maybe a couple more mics in the future, but I'm basically looking for a simple setup where i can stream quickly without much set up hassle.

I can not reply to all of your questions, but some remarks:
Get a professional camera-app that allows you to see the audio levels like - for example - Movie-Pro. Movie-Pro is what I use, but there could be better apps out. Just have a look. These are 20,- or so.

I don't know for sure if what you want to do with your audio AFTER entering the phone is impossible

https://forum.audiob.us/discussion/2...audiobus-input

, but I would go another route:
Make sure that the audio that gets into your iPhone is the audio you want. Mix it and add effects BEFORE it enters the iPhone.
I own the H6, but I guess that the H5 allows mixing, too. So mix on the Zoom.
The Zoom H5 already has build in compressors/limiters with different settings among others for vocals.
Use a reverb you already own or get something like the MicMechanic from TC for your vocals.

Yeah, I know I can figure out several outboard ways of prepping the audio. Just seems idiotic that one couldn't do it all in the box.

I'm not aware of a video-recording app for iOS that allows you to input processed audio from another app on the same phone. There are several that allow you to input audio from an external interface. This looks like an opportunity for someone to fill this gap, and someone no doubt will (if it's not already available).

I wonder if, for a more compact outboard solution, you could use a secondhand iPhone or iPod touch to run an audio app to add the effects you need, and send that processed audio back into the Zoom and then on to your iPhone that's recording video, rather than having to use something as big as a laptop or your Mackie mixer and a separate reverb box? I'm not sure it would be possible given that these devices have just one input/output but it would be a compact solution.

Seems so.

Yeah, I have an older MacBook I could use as a dedicated ITB mixer. It's small enough but of course the hassle of transporting/disconnecting/reconnecting the audio interface. Fine for my home setup and doable for mobile. Just would be better if all I needed was my iPhone, Zoom, and mic(s).

Like I proposed before, get something like the mic mechanic from TC and you have all you need. I wouldn't hassle with another iPhone or notebook. If you are not only the artist but the cameraman and recordist, too. There are too many devices to set up and to control in the other setups.