according to the website it looks like it came with a USB adapter, if your mic is bleeding through aux, use the USB.
for whatever reason realtek in my experience fucking hates microphone line in, especially if you're doing what i think you're doing and running both audio out and audio in through one cable.
also im assuming if it came with software, the software would probably work better anyways with the USB connection as opposed to the 3.5mm
if you don't have the USB, USB soundcards are like 20 USD on amazon, but given that the headset is like 80 bucks on its own, maybe its better to just live with it and try using discord's baked in stuff