Some updates with my NAD T778 experience:
Hdmi 2 will not output any signal if 4K goes out of Hdmi1 already. But if the 4K thing is off, then a AppleTV will not see a 2k Display on HDMI2 and switch resolution. (hence no AppleTV Atmos w/o 4K display). The NAD does not do anything to the hdmi signal, not even amplify or recondition it as an Oppo or any Chinese box does. Hence the hdmi cable length adds up: Meters in and meters out. The three meter limit where 4 k gets sometimes messed up comes quickly. If the 4 k length is ok, but the cable to a 2k monitor on hdmi 2 is bad, then the hdmi 1 out becomes a gamble. Gets messy quickly. Not even throwing in ARC yet…
Backchannels need to be assigned to the amp output if they are used. If Height2 or Zone is assigned instead, then there will not be any backchannel nowhere.
AirPlay via IOS does not carry an Atmos Signal. (Nor does IOS into a first generation 4K ApppeTV)
Having no Webinterface is a joke. Having an IR remote instead of a wireless is another one. Not being able to save ones NAD setup to an USB stick for retrieval after a factory reset sounds like Stone Age. I guess NAD is short of software engineers...
There are more inputs than source selectors. One would have to bundle HDMI and analog to make all work.
An 12 V trigger signal can not be assigned to the listening mode, like stereo or Dolby, but only to the source.
BlueOS seems to capture a Roon stream and presents it in the App as „his“. I guess the Roon guys do not like it, hence it is „ready“ only. But an incoming Roon connection does not trigger the BlueOS‘s source assignments (listening mode, trigger) but „hangs in the air“ unassigned.
The NAD should stand freely, then the fan stays low
It is a very nice, modern box.