That M.2-like port at the bottom is actually the audio circuitry, and the “heatsink” is just a fascia. Only the custom audio board will work in it, and Asus specifically prohibits using anything else, stating it could damage the board. The audio itself is a typical Asus-tweaked Realtek ALC1220 codec dubbed SupremeFX and sports an ESS Sabre 9023P DAC.
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