I have read that some of the newer Zidoo players support HDR and Dolby Vision, but Dolby Vision is not listed directly on the website. You may want to email them to make sure.
As far as I can tell, Dune and Zappiti do not have Dolby Vision yet. These are somewhat small companies (not like Marantz/Denon which have a team of 80+ engineers). New technology updates are always a challenge to keep up with. But you should ask yourself the question as to what's more important? New features and functionality? Or overall audio/video quality. A lot of content from Netflix/Hulu/etc. is not going to be in HDR or Dolby Vision anyways.
As far as I can tell, Dune and Zappiti do not have Dolby Vision yet. These are somewhat small companies (not like Marantz/Denon which have a team of 80+ engineers). New technology updates are always a challenge to keep up with. But you should ask yourself the question as to what's more important? New features and functionality? Or overall audio/video quality. A lot of content from Netflix/Hulu/etc. is not going to be in HDR or Dolby Vision anyways.