For those who have been wanting to use the old 4K Joeys to access 4K HDR content, there may be some workarounds to help with that. I am not sure if these methods have been mentioned before, but I just found out about them today on the other forum. Thanks to a member there named GStill:
If you use Game Finder to find the 4K game, and get the pop-up telling you that the game is about to start on channel 540, the 4K Joey will tune to that channel and let you watch the game in 4K HDR. The catch is that you have to leave it on that channel the entire time. If you change channels, the 4K Joey will not let you tune to channel 540 again.
Another option is to record the 4K game on the Hopper 3. If you transfer that recording to an external hard drive, then the 4K Joey can see and play that recording in 4K HDR from the EHD. This is despite the fact that the 4K Joey cannot see that recording while it is still on the Hopper 3's internal hard drive. This is not as convenient as being able to watch the games live on the 4K Joey, but at least it shows that the 4K Joey is capable of playing 4K HDR content.
I will note that the poster who made the above suggestions is using a Samsung 4K HDR TV. There is no guarantee that the 4K Joey will work with other TV models the same way. However, it is still something worth trying, just to see if it works.
Also, I may not be remembering this correctly, but I thought Scott posted quite awhile back that the 4K Joeys could also play 4K HDR content from the Amazon Prime app. Clearly, the 4K Joey is capable of playing 4K HDR content, at least under some circumstances. It is still a mystery why the 4K channels for live events (540-xx) do not show up in the guide on the 4K Joeys.