Thanks for making and supporting Volumio.
It is a pretty good setup on my Raspberry Pi, and the interface is easy to use and mostly intuitive.
My setup includes a Raspberry Pi 3 outputting I2S via GPIO to an outboard DAC of my own construction.
The sonic path is Volumio/Pi -->homebuilt DAC [SRC4192 sample rate converter -->PCM1794 DAC -->passive I/V --> tubed balanced-to single ended stage] --> tubed preamp -->Modded Dynaco ST-70 amplification -->Martin Logan Electrostatics.
While there are some issues with usability, navigation and general usefulness I’m sure these issues will be addressed in the course of time.
All the best!