Do any players support Dolby Vision for local files?
No there is not. The previous reply mentions something with illegally cloned HW provided with hacked FW and sold from below the counter only.
Sure there are. The latest Nvidia Shield does support it as well as the ATV 4K and I'm playing DV profile 5 (single layer) files just fine with the ATV 4K from my NAS.
One could argue that these are streamers rather than media players, but the lines a blurry these days and the Shield can pretty much do everything that a media player can.
However "Dolby Vision support" doesn't really say much. The supported profile is very important. While profile 5 (single layer) is used for streaming content, profile 7 (dual layer) is what the UHD BD uses.
The SoC definitely supports DV. However, I don't know which profile. It
could be both if the SoC is also meant for UHD BD players. While Oppo, Pioneer and Cambridge all use the same MediaTek SoC I don't know what Panasonic is using (most likely some sort of custom MediaTek SoC) and UHD BD players are not really flourishing anyways these days so its not that likely that the SoC is meant for those players.
That said, afaik Dune needs to negotiate directly with Dolby. So if they don't come to an agreement it doesn't matter if the SoC supports it or not. While they can argue for implementing profile 5 (as there are legal reasons for it), the argumentation for profile 7 will be very difficult as there is not really a legal way of playing those files.