One question though:The guide mentioens that “Zones can only be grouped with other zones of the same type”. I guess my Mac creates a RAAT type zone because it’s macOS, but the guide doesn’t say anything about iOS, i.e. my iPad.
Does anybody know whether the app on iOS creates RAAT zones?
It will tell you what they are where you go in to authorise them. Some like a MAC might present more than one way to authorise, for instance system output and a sound device like a DAC in addition to AirPlay. The one you chose will tell you what it is.
It’s enabled by default on mobile devices because the assumption is that, most likely, playing to those devices will be only controlled when using the device itself (e.g., for headphones) and not as a part of a zone from another device.