Same problem here that many others are having. I have the Shield Pro 2019 going through a Denon Dolby Vision compatible receiver to an LG C8 OLED and I can’t get an MKV with DV to trigger Dolby Vision (it just plays regular HDR10).
Edit: looks like I got it working. I’m not sure what I did but one thing for sure is having to go into the Shield resolution settings and making sure the output mode is set to 4k @ 59.94Hz with DV and HDR10, and also toggle the Dolby Vision switch on in that same screen.
I didn’t have refresh rate switching or anything else like that on in Plex.
