enthusiasts aren't necessarily using the onboard DAC. plenty of small external DACs exist that can receive a digital audio stream over the phone's USB.
I use the dragonfly red, a fantastic dac and amp that was significant upgrade over the built in phone one.
I’ve tried the Dragonfly on my phone and tablet and it was very unstable, and to my knowledge it was the only one to buy from friends who are far more knowledgeable on that than me.
I use it with the excellent USB Audio Player Pro. It uses its own driver for external DACs, I guess because the Android one is not fit for purpose.