Well, thanks to the builder's research, it turns out that the RPi-DAC setting works well with this, although he did say that this *has* to be set on the initial installation, else Volumio GUI shows that the DAC is changed but doesn't change the driver. I shall run the thing in and see how it goes but it sounds good already...
Can you share your full impressions of this DAC's sound quality after using it for a couple months?
To my knowledge, there is only one other multibit RPi DAC hat out there, and its the one I use in my system now. I'm talking about Matt Garman's TDA1387 hat. I have tried several DAC hats in my setup, including Boss, Piano, PecanPi, DIAL, and the Audiophonics TDA1387, plus a couple DIY prototypes. The Garman DAC is my favorite of all. https://www.diyaudio.com/forums/digital-line-level/313395-tda1387-dac-pcb-front.html
Anyway, I seem to much prefer the NOS sound. I have never heard an AD1865 DAC, but these chips seem to have been used in some top-tier commercial gear in their heyday. This new DAC hat definitely has my attention! I look forward to hearing more about your experience with it.