I can confirm Sabrent USB Audio Stereo Sound Adapter AU-MMSA works on back USB as Audio Input and output. You can use it to plug in an external Mic or Mixer and Speakers or headphones.
TESTS with the USB Sabrent:
I used a Sony Lapel Mic on the pink (mic input) (Good Sound but low).
I also plugged in a ZOOM H4n Pro to the AU-MMSA USB Sound adapter (pink plug) and was able to control volume of my 4 mics connected to the ZOOM H4n Pro (I Guess this would work also with other types of external mixers)
PROBLEM You cant use USB Web Cam Logitech 920C at the same time. (Im guessing this happens because there is only one USB AUDIO (Beta) Input, and that is ALSO used when you plug in the Logitech Web Cam 920C that has a Mic input…I will try with a USB Cam with no MIC and see if it works.
CONCLUSION. It is a Cheaper or alternative option for EXTERNAL Audio input instead of a HDMI Switch Inserter. I still have to test Audio Latency with two HDMI Cameras using a Seamless Switcher Im expecting to arrive soon.