Hey I found the solution to this at the bottom.  It's a Samsung EE-UC10JUWEGUS USB-C to 3.5mm Adapter (not an external sound card like the one shown below but an adapter that goes directly to the board - just like the "Real Mccoy" but it's replaceable and only $15) https://www.samsung.com/us/mobile/mobile-accessories/phones/usb-c-headphone-jack-adapter-ee-uc10juwegus/ ... View more

Problem Solved! Solution: Samsung EE-UC10JUWEGUS USB-C to 3.5mm Adapter - https://www.samsung.com/us/mobile/mobile-accessories/phones/usb-c-headphone-jack-adapter-ee-uc10juwegus/ This is a direct 3.5mm Stereo with Microphone (T-R-R-R) to USB-C adapter specific to Samsung S21 Ultra and turns your USB-C jack into the actual headphone jack that would be on the S21 board (if it were built in). The problem with the adapters shown above is that they are essentially USB sound cards - which would mean they would require external drivers.  Some of these are made for PCs and don't include Android drivers. Thinking about the whole thing, it might be better to have this adapter than a headphone jack on the board.  I have always ended up having to clean this port, since stuff gets into it like lint in your pockets. I don't like how you can't charge your phone while listening - however from an engineering standpoint there is a physically possible solution to this too, and if I find it I'll let you know ... View more