You cant use embedded DAC over USB C because DAC only output analog signals which USB-C can’t** transfer. I actually have LG G6 (Korean version with QuadDAC) and when I used with any USB-C earphone (Xiaomi one) it switch to earphone DAC.
btw iphone still have a DAC since it still has speakers. And DAC on lightning dongle is one of the best DAC available to drive <100Ω headphones and for anything else (240Ω) you need more professional grade DAC with strong amps. [Dongle DAC analysis by kenrockwell](100Ω)
** USB-C standard specifies an interface through SBU pins to transfer analog audio however pins are inactive on every android phones/ (PC too I think) since it can easily interfere with digital signal causing distortion to both of them.