Multiroom receiver cannot be enabled with I2S device

[Tim Curtis]

The rpi-dac driver does not support Hardware volume. What audio device are you using?

The help text from the Receiver section of Multiroom Config is not clear on what exactly is meant by "supports Hardware volume". 

Code:

The Receiver requires an audio device that supports Hardware volume.
NOTE: Volume type must be set to Hardware or Fixed (0dB) in MPD Config.

It should prolly read something like below. I'll update it for upcoming moOde 8.1.0.

Code:

The Receiver requires an audio device that shows "Hardware" in the Volume type dropdown in Audio Config.
NOTE: Volume type must be set to Hardware or Fixed (0dB).