[Qerub]

> […] Airfoil software does all this & more […]

Not quite; Airfoil Satellite does not implement an AirPlay 2 receiver which is what this is all about. See https://weblog.rogueamoeba.com/2018/06/25/current-notes-on-a... :

> Can Airfoil Satellite receive AirPlay 2 audio? Airfoil Satellite receives audio via the AirPlay 1 protocol. Because of this, it can’t currently be part of a multi-speaker group receiving audio from iOS.

Still a great piece of software (that I also can recommend).