I think standard depth on that kind of stuff is 18 inches or so. AND THEN you will want extra space for ventilation.
It appears you are very concerned with install. Which probably precludes you from using 2 fans, one for intake other for exhaust, which your unit might very well need.
I know of no AV receiver that shallow, and have never seen on on-line or in person. Sorry.
For the rears, if they HAVE to be invisible, in-walls are still better than in-ceiling.
ear-level > in-ceiling > in-wall > nothing
Putting new home theater system in new room and will place receiver on built-in bookshelf. Want a high-end receiver but don't have much shelf depth - only 15 inches from front to brick wall behind - that's after extending it. Will be routing cables/wires through brick wall (into garage) and back through to TV to keep wires/cables hidden. Hard to find depth specs for many recommended receivers so thought I'd see if there are any recommended ones that are not more than about 13 inches.
Also planning ceiling mounted speakers for rears - any bad drawbacks?
Thanks in advance!