Dear Siva,
I beg to differ with you on HDR impacting overall experience and picture quality. On the contrary, i have LG nanocell uhd tv, supprting hdr, hlg as well as dolby vision and I'm pleasantly surprised with the hdr being available all the time on my xstream box. Perhaps a bit of tinkering / calibration is required if one finds luminance levels to be slightly on the higher side. But even the sdr content looks great with hdr on, colours have more depth and there are fewer darker spots on the screen. Even though the colours are in 8 bit, still they seem quite vivid when compared to regular sdr content. The conversion of non sdr to hdr is working out excellent for me. I've stopped watching content on official lg store apps
(hotstar, youtube, prime video, Netflix - only sdr content not the one with Dolby vision support, dlna steamed movies etc).
One more thing, hdr only kicked in for me once i changed resolution in display option on xstream box, to 4k. It was not available with default resolution. I truly and sincerely hope that this feature doesn't go away, as hdr can be turned off locally in every tv setting, by simply disabling deep colour / Enhanced signal (or whatever it is called in other TV manufacturer models), but can't be turned on the way it is available right now.
@parag - to disable HDR on your lg tv, you simply need to disable deep colour for respective hdmi port in your TV settings. Follow this path, settings - picture - additional settings - hdmi ultra hd deep colour - toggle off deep color for respective hdmi. But... Try with hdr first and calibrate your screen a bit, it should work wonders.
Cheers.