IIRC the 4K Firestick does support Dolby Vision at 2160p50/2160p60 but because the TV only supports DV at 2160p30, at best, it will only output HDR.So it's a UK 50fps frame rate issue that gets HDR instead of DV. If I watch Netflix via my 4K Firestick, the default settings give DV but restricted to1080p. If I manually set it to 2160p 50 I get the same 2160p but HDR as the inbuilt app.
Just-so-you-know... It's only the 2016 models that have the maximum '30.000fps' Dolby Vision limitation....I've noticed that more Netflix shows seem to be playing in HDR rather than DV on my 49UH850 than did so previously. Meanwhile on my 49SK8500 in another room they continue to play in DV.
Interesting that they run the same software as the OLEDs. I suppose that explains why mine seems to do some sort of compensation cycle every so often (about once a fortnight).Indeed... The (2016) UH850's and UH950's run using the same software as the (2016) OLED C6's and OLED E6's