Ditto on ATV 4K and Atmos. Its a great bit of kit, with an excellent selection of 4K movies with HDR, mostly Dolby Vision
. It also has noticeably better Netflix and Prime players than my LG E6 (better FFW/REW behaviour mainly, not critical, but nice!).
I believe the 2017 models default to Mode 1.
Mode 2 makes sure people will at least get a picture if they hook everything up with some old cable that cannot do the higher bit rates available with HDMI 2.0. I think, in the early days, they were worried about a lot of supports calls! But, I agree, at the very least they should have put a really big sticker right up front in the manual explaining this setting and saying it needed to be changed for the full UHD experience, including HDR. Even the AV specialist I bought mine from was unaware of this setting (16 months ago) until I found out and told him! It also doesn't help that the description in the manual is simply wrong
! It says it affects only 4K/50 and 4K/60, suggesting it only prevents the most taxing 18Gbps modes, but in fact it stops all modes over 9Gbps, so preventing proper playback of all UHD Blu-ray, most of which are 24Hz