Not sure if this is the right place, but just got a 3080 today. My r9 290 booted with a DVI cable to DVI and had no issues displaying both monitors. When I went to bring up my current dual monitors, I ran into issues. 
 
Connecting into Green circle port has no issues. If I connect into the next port with the same cable, I lose the signal. Not sure if this is normal or if it is sequential in nature. Like I need to fill green circle before I go onto next port to have display.
 
The Red circle is a DVI cable (monitor) to HDMI (GPU) and the monitor doesn't even show up. When I unplug the display port cable from the green circle, the DVI monitor flashes solid colors over and over. When I plug it back in, it goes black. In the Nvidia control panel, it shows the monitor, but will not let me toggle it. I updated my video drivers, but am getting nowhere. Any help would be appreciated. Thanks!