Hi Did you find a solution for that?
I found that in UE4.27 there is a permission setting in Project Setting->Platforms Android → Advanced APK Packaging → Add Permission to Support Voice Chat (RECORD_AUDIO) = True.
I think that is required to be able to use the Mic Input through Audio Capture. Unfortunately, I can’t find a way to acknowledge that permission as a Developer Mode in my Quest 2, anyone managed to make this work?