As far as I understand it isn´t possible at the moment to group different kind of endpoints. So in my current situation it is in fact not possible to set a group with the Deivalet AIR and the RPi for example. But the other threat isn´t clear about the possibility to group same endpoints like two Rpi´s. Before I will buy a second one, it would be nice to know if this is really possible (Syncronize multiple Roon outputs)