@djnice
because there is a slight difference between the Dolby Vision profiles (profile 5 or sometimes called ‘single-layer’ vs. profile 7 or sometimes called 'dual-layer). In other words: DV is not equal DV.
@sixones never stated that “dual-layer” would be supported… he said that that DV will be supported.:
Even if Plex would support “dual-layer” DV, you would never play such content on your Shield TV 19 since it only supports “single-layer”.
Furthermore, I requested support for dual-layer and one of the developers stated that Plex will never does it.
You will have to make your own single-layer DV content from e.g. your original UHD Blu-Ray (there is software for that; e.g., DVDfab… and there is a huge debate on that topic out there.)