As can be seen in this and many other videos it is possible to connect a USB mic like the Zoom H1n or Blue Yeti to an android device and use it as default audio I/O - but on m FP3 I don’t see this option as described in the video (developer options->default usb configuration). Audio simply doesn’t appear, any ideas?
Android support for USB microphones is quite spotty. I think most of the blame lies with USB microphone manufacturers who aren’t particularly adherent to settled standards.
All I can tell you is that I tried to connect a Blue Yeti to my FP2 some time ago, I jumped through hoop after hoop, tried every trick I could find and think of, but as far as I can tell from reading dodgy forum posts and Yeti’s own online info, the Yeti only works with some Samsung phones.
FWIW, you can get the Yeti Pro, which has analog output which can always be trusted to work, with any device. Love those international standards.