Yes I consider that the box requiers a fix/update, because I tried a lot of boxes from other brand and with all others brands I can change this setting it's not greyed.
Here attached the picture of U5 (setting greyed) and picture from other box (free choice of settings)
Both boxes were on HDMI 1 port, with the same HDMI cable.
If I post something, it's because I tried everything to resolve the issue and I am sure at 99% that the problem does not come from my side.
For me it was obvisous that the box support HDR, I did not ask myself if latest generation box support HDR or not.
And my comments / requests are from improving the Buzz box, I like the boxe and I see a very good potential, but some stuff need to be improved. Because competition has also great products and I will be happy to see buzztv as number 1.
Thank you for your answer.