USB

I plugged my phone (S8) running Android 8.0.0 into the USB of my Benchmark DAC 1.
I did so using an adapter (USB C to A) and an A to B cable.

The Benchmark DAC 1 is a UAC1 device.
This means the USB audio is limited to 24 bits / 96 kHz max.
Started Foobar mobile and without any adjustment or configuring the DAC started to play.

 

In Foobar I activated the re-sampler and set it to 96 kHz, the highest available rate.
Music kept on playing.
It look likes Android 8 support 24 bit / 96 kHz audio.

Host mode

Android 5.0 (API level 21) and above supports a subset of USB audio class 1 (UAC1) features:

Host mode is USB audio as we know it when connectiing the DAC to a PC.

The PC (or in this case the phone) is the host.

Powering the DAC might be a problem.

This can be solved by using a powered hub.

 

Old Android devices have a micro-USB connector that does not permit host operation, an on-the-go (OTG) cable is required.

OTG

USB Audio Tester

A little app by Daniel Sobe available on Google Play

 

Select the USB device, in this example my Benchmark DAC 1 USB

 

All the sample rates supported by the USB receiver of the DAC are listed.

 

 

Third party

USB Audio Player PRO has its own implementation of USB audio.

References
  1. USB audio - Android Open Source Project
  2. PulseAudio vs. AudioFlinger - Arun Raghavan