Most of my 4k viewing comes from both Netflix and Amazon Instant via the Nvidia Shield. The youtube App on my my Sony TV and Shield do not support HDR at the moment. Some of the videos found on Youytube, I'm able to download from 4k websites, stream them through Plex or Kodi, and I'm able to view them in HDR in this manner.
I did watch Fantastic Beasts a few weeks ago via Vudu, with Dolby Atmos (lossy through Vudu) and it was a good experience.
A good portion of Original Series provided by both Netflix and Amazon Instant are in UHD, and some also provide HDR as well.