The Galaxy S8 and the G6 LG are the only mobile devices capable of playing quality 4 K UHD HDR video content. Unfortunately, this function is not compatible with Netflix.
The contents of video with the best quality you can find currently are in the Ultra HD HDR format. High dynamic range for the videos is reflected in scenes with a greater range of colors, a few stronger contrasts and many other improvements. Unfortunately, the contents available in this format are very rare now, but Netflix is among the few companies that provide it.
Netflix, no support for Ultra HD HDR video in smartphones
Although the new Galaxy S8 and LG G6 4K HDR video playback support, the bad thing is that no you can take advantage of this function unless the supplier of the videos or streaming platform has videos to that format. In other words, no good for anything that has an agreement signed between the manufacturers of smartphones and Amazon Video, if Netflix movies HDR may not be reproduced in this format, for now.
In theory, if you are using a S8 Galaxy or a LG G6 you should be able to play videos 4 K HDR from any online or offline source. But in real life, at least when it comes to Netflix, streaming platform says that these Ultra HD video playback is only available for a few TVs and monitors, without having plans for now to extend this functionality with smartphones.
For now, Netflix ensures that mobile devices might receive in the future videos UHD HDR support, although the exact date of its availability is not known.
The only thing you can do is wait, or subscribe directly to Amazon Video to surprise your friends with spectacular Galaxy S8 or G6 LG screen. In what concerns the variety of quality HDR Netflix content, platform now houses only about 20 films in this format, so there are too many reasons for frustration.