I do not see why AVR would not decode and play sound if no display attached, makes no sense to me, it should be in passthru mode or something like that or just AVR need a reset, same for the EDID being reported as 1080p, may be wrong input or AVR needs a reset.The AVR manual link was in my first post, but it doesn't tell you much. It supports 4K60 444 but not HDR (so HDMI 2.0) and no HDCP 2.2, for inputs, outputs and upscaling. It also supports Deep Color and xvColor like the PJ.
I guess it is reporting 1080P60 because this is what the connected PJ supports (manual also linked in first post). Note that if I don't have the PJ connected, it goes from 8b to 12b, but still 1080P60. I guess that this means that it won't report its 4K capability until you plug in a 4K display. This is even more bizarre, because, according to the manual, if you give it a 4K source, it can only provide a 4K output.
The fact that the PJ reports 1080P60 8b seems to be a mistake (by Sony), seeing as it supports Deep Color / xvColor. When I manually scale, setting the bit depth to anything other than 8 makes the picture disappear. Time to give up on this one.
The bigger problem with splitting audio and video (and feeding the PJ directly) is that without a connected display, the AVR won't give any HDMI audio.
So I'm back to square one, using the Integral2 to downscale 4K to 1080P 8b and feed it to the AVR, where I still get DD+. Still no sign of Atmos, even though I see Ultra HD reported as Jack Ryan / Carnival Row play.
@claw Regarding Ultra HD on the Fire Stick 4K, it seems that the Fire Stick fixes its output resolution according to the reported EDID (if left on Max), and when you play content marked UHD (e.g. Jack Ryan, Carnival Row) it dynamically switches between resolutions according to available bandwidth. So watching the same selected item, in the status it could say Ultra HD, then later HD, then later 1080P HD. The output mode doesn't change as this would disruptive causing a display re-sync. Instead it must up-scale to the fixed output resolution.
Thanks for your help.
I suggest you reset AVR, connect as i recommended with split output and export config if it doesn't work and add it as attachment.
I'll check AVR manual if needed after our config export.
confirm which AVR input you used for the config export you will supply.
Similary if PJ is supposed to support deep color, may be it's only from a particular input or may be there is option to set for each input for that.