I did a search as you suggested, and holy cow, did Sony mess up. Claiming that everyone else has to update their products to with the a Sony TV. Sheesh. I had no idea they did something so messed up.
I guess we'll just have to wait until someone actually tries the new Ultra on a Sony TV to see if it accepts a DV signal. Since the Sony problem is two years old now, hopefully the Roku engineers were aware of it and have tested it out.
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It's looking like it currently is only supported 4k 60hz dolby vision. People with older tv's that only support 4k dolby vision at 30 hz or such are being forced to use 4k hdr or 1080p dolby vision. I have an older LG OLED for 3D support so have no plans on upgrading. Will be returning the ROKU.