Just adding this little tidbit in case it helps anyone.
TL;DR Boot order of the gear matters.
In my HT, my PJ is still a 1080p with FauxK (JVC 4810), so I need to fool the ATV4K that my rig supports 4K, or else Netflix and others do not offer Atmos soundtracks.
To achieve that, I use an adapter (
https://www.amazon.com/gp/product/B07VP37KMB/) that does EDID spoofing to fool the source into thinking it sees a 4K device.
It also is a splitter, but not used as such in the HT, strictly used to convince the ATV4K that I have 4K support, and thus gain Atmos.
But, when I fully power down (zero AC available) and back up, this adapter boots faster than my Marantz preamp, so it does not cache the EDID from the Marantz that it does indeed support Atmos. Thus the ATV4K refuses to offer up any Atmos content.
To fix, I just pull the power from the EZCOO adapter, and when it comes back up, it is able to pull the EDID from the Marantz and then on the handshake with the ATV4K, it is told we are a 4K device that supports Atmos audio.
Usually, none of the above is an issue because I put the system into standby (for the sources, amps are fully powered down). But every month or two, for one reason or another, a total power loss happens, and I have to reboot the adapter.