I've read on reddit that playing HDR content directly with LG native player produce better quality, how ?
Upstream Linux supports static formats like HDR and HDR10, not dynamic formats like HDR10+ and DV, so other player apps running on other OS e.g. Android with vendor kernel that includes magic closed-source binaries for DV support, or a good physical media Blu-ray player that similarly supports dynamic HDR types; should/could in theory give better results than e.g. LE running on an old NUC that does not.
Also what is the difference of using this NUC to play a 4K UHD BD Remux in HDR and using a good bluray player like panasonic UB820 with same UHD media but on physical disk ?
Some users will insist they can absolutely tell the difference and there is a multi-billion dollar industry designed to relieve them of $$ in the pursuit of "bit perfect" quality. That said, the entire concept of "bit-perfect" doesn't exist for video due to how original media encodes a suggestion of how to show things that is then interpreted by an imperfect display device, e.g. no TV in the market actually supports 10,000 nits brightness, so even if the source media is perfect the output that you see is always some kind of best-efforts compromise.
Ripping media to anything other than ISO results in format conversion and this is always a lossy process. Most users are happy with some quality loss for the convenience of having their media in a software format, and with HEVC and AV1 offering smaller filesizes than H264 and particularly ISO, for a "perceptually similar" level of quality, most users are happy to avoid the need for many TB of HDD space. I do find it amusing that the "bit-perfect" crowd found on Reddit and Android forums espouse on how perfect their system is when logs show their source media to be some remux torrent with totally unknown encoding.
Most users are just happy with the HDR logo lights up and the display and colours are brighter and things generally look better than a boring old SDR movie. Most users over the age of 40-years are also subject to some level of macular degeneration.
"Don't believe everything you read on the Internet" -- Abraham Lincoln
