USB-C External Microphone doesn't work on Clubhouse or in any chat application

Have you checked Settings>Privacy>Microphone, and see if Clubhouse appears in the list, and if it does, is the microphone turned on there?

I don't think it's solvable, because I think it is someone, weirdly, and maybe unintentionally, a Clubhouse "feature," i.e., the problem is that Clubhouse itself disables the microphone, as you said.

So, with a single pass through cable, I can (1) hear Clubhouse with the monitor jack on the microphone, while I (2) use the microphone (with the easy-to-spot reverb prset) to successfully record on the voice app....but (3) only the clubhouse microphone voice with reverb records.

So, I'm hearing an audio out signal generated through the phone all the way to the iocrhpone output, but the voice app will only record me and the mike.

And certainly, it doesn't work at all if I try to use it on Clubhouse directly.

What a mind-f**k! Maybe Sonus might have an answer.

You allow microphone access to individual apps, not just a single switch. And, the native Apple apps do not require permission, however, 3rd party apps such as this Clubhouse do. I did not see you mention that voice calls did not work. Or are you referring to something other than the native phone application?

I read your original post, I was just confused when you mentioned the 3rd party app, but then you say that the problem was with voice calls in general. So I was confused if that mean a normal cellular call as well, or if it was just with apps. At that point, since I don't use that app, and since it is not an Apple app, I would suggest contacting their support about how it may interact with external microphones. And you would probably do well to contact the mic manufacturer to ask them about the iPad using their device with 3rd party apps as well.