HDR video is still a fairly new type of media, and it's certainly going through its growing pains at the moment. Content is sparse, and adoption is even less present, both by consumers and by manufacturers. Creating HDR content is a very intensive process, and is often done through tweaking in post-production, making it mostly impractical for small creators, and even a drain on big media providers and creators like Netflix. HDR will likely grow as the technology gets easier and cheaper, and those with certain Samsung TVs will find themselves ready. They will find themselves so ready, in fact, that they should already be expecting an update, if they haven't received it already, that allows their TV to play what little HDR content is on YouTube in all of its glory, and without any additional fuss.
A good portion of Samsung's 2016 TV lineup, being their range of Quantum Dot and UHD TVs, are compatible with HDR content. Those TVs are mostly already able to access YouTube and its wealth of content through a dedicated app, but an update to the TVs, which is already hitting some TVs and will be making its way out to all owners within the next month or so, will allow access to an upgraded version of the YouTube app that can play HDR content. Functionally, the upgraded YouTube app that owners will see is no different from the one they're currently using. The kicker is in opening the door to the growing world of HDR content.
YouTube features a dedicated HDR channel, which is currently a bit light on content. There are a few 4K HDR playlists that one can find by searching, all of which have yet to exceed 100 videos, and mostly consist of content made primarily as eye candy, like nature shots. Owners of qualifying Samsung TVs can find the good stuff by heading to the 4K channel within the YouTube app. If their TV is up to date, the content in the HDR sub-category will play as intended, with all of the insane quality and fidelity one would expect from 4K HDR content.