Hello,
Finally got a 3080 through the queuing.
I'm having an issue with Long Optical HDMI cables and my new 3080 XC3 Ultra. It will not pass any video through HDMI, oddly enough, windows does show EDID information and shows that it's connected, but the TV (Samsung 65 KS8000) will not display an image.
I am able to see that info when I connect a 2nd monitor through DP. I also tried connecting the same monitor at the display side to check if its the TV. I get the same result with no image displaying on the monitor.
Next step in trouble shooting, I connected a short cable over HDMI to my monitor and that worked fine. So the HDMI port seems fine from the 3080 with the short cable. 
So maybe I have an issue with my Long Optical HDMI cable. I decided to test my work laptop, its a Dell Precision 5540 with HDMI 2.0 port, and that worked fine with my optical cable to the Samsung display.
 
Next steps was trying 4K30, 1080p60 and none of those would pass with the optical cable with the 3080.
 
Reason for long cable is that have a rack mounted gaming PC in the rear of the living room and running a cable all the way to the display in front of the living room so I need about 50ft of cabling.
 
I do have 25ft HDMI cable i was using in the bed room   This cable did work but had some issues. I was able to get 4k60 HDR 444 out of this one, but I do get a random blank screen every once and while.
 
I currently had this 60ft Optical HDMI Cable that supports 18gbs 4K60
*cant post links, but its Celerity Optical Cable with HDMI adapters
I had no issues with my Founders Edition 1080ti with the Optical HDMI cable
I decided to try another cable so I bought this one from Amazon
* cant post links, Amazon Basics 50ft Optical 4k60 18gbs
I get the same exact results with the amazon cable, no video from this cable.
 
So here is the weird thing, I happen to have DP1.4 to HDMI 2.0 adapter that use with my work laptop dock 
 *cant post links, Startech DP 1.4 to HDMI 2.0 adapter
And this adapter does work with the HDMI Optical cables, it worked with both Celerity cable and the Amazon Basics one.
I hate to buy an adapter for this to work, but obviously there is some sort of signal issue with the 3080, not sure if anyone has come across this. I am wondering if there any other settings may be missing on the Nvidia drivers.
 
 
 

Is the card trying to send 4K120?

Quite the stretch.  This should be able to get you where you want it with an ethernet cord though?  Maybe something research anyways.
 
Amazon.com: gofanco 4K HDMI 2.0 Extender Balun Over CAT6/7 Ethernet Cable – Loopout on TX, Up to 230ft (70m) at 4K @60Hz YUV 4:4:4, HDR, 18Gbps, HDCP 2.2, Dual IR, Toslink Audio, Near Zero Latency (HD20Ext-Aud) : Electronics

Just browsing around and I can see that this is an old thread but you have returned with an update.
 
Thank you for updating us, so many people have issues and then never report back.
 
So I appriciate you dropping in to let us know.
 
Happy days with your new 3080