Ok I got it working 
So before I was taking a video on my iPhone 12 Pro and then going to my iMac where the video would be automatically synced using iCloud. Then exporting the .MOV file onto my Synology NAS and playing from my LG OLED 2019 C9 TV. Using various app's on the TV or even Airplay directly from the iPhone it just WOULDN'T work
So to make it work ......
I took a video 4K 60fps HDR and saved the file directly to my iCloud share from the iPhone. Cutting out the iMac and Photos app. I then copied the .mov file from my iCloud drive to my Synology NAS and BOOM. When playing in either the LG native media player or Plex the DV icon is top right on the screen and works
Using the mediainfo application I can see the video has HLG now
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Correct I got it working....see my post above...
So before I was taking a video on my iPhone 12 Pro and then going to my iMac where the video would be automatically synced using iCloud. Then exporting the .MOV file onto my Synology NAS and playing from my LG OLED 2019 C9 TV. Using various app's on the TV or even Airplay directly from the iPhone it just WOULDN'T work
So to make it work ......
I took a video 4K 60fps HDR and saved the file directly to my iCloud share from the iPhone. Cutting out the iMac and Photos app. I then copied the .mov file from my iCloud drive to my Synology NAS and BOOM. When playing in either the LG native media player or Plex the DV icon is top right on the screen and works
Using the mediainfo application I can see the video has HLG now
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Found this pic (and the video) in a russian forum. Looks like the C9 plays it as DoVi.
View attachment 973405
Correct I got it working....see my post above...