My GPU has 4 ports on it. DVI-I, DVI-D, HDMI, & DisplayPort. It is the DVI-I that I have always used so that it will work with my VGA KVM via an adapter on the back of the card. Even though I never had issues using it before I swapped motherboards it is this port that always goes black as soon as the login screen comes up with this new motherboard. I decided to try and test the other ports by running cables to my TV as a mirror. Using HDMI on my monitor and then plugging a DVI-D to HDMI cable to my TV and it said it was unsupported until I changed resolution and it worked but both displays are identified as my monitor. I also ran a DisplayPort to HDMI cable to my TV and it worked as well after changing resolution but both are also identified as my monitor. I then tried running a DVI-I to VGA cable to my TV but it says there is no signal and no mirror options come up.
I also tried swapping monitors thinking that maybe it wasn't displaying because the resolution was defaulting too high as the monitor is at 1920x1200 which my TV apparently doesn't support. So I plugged in a smaller 1080p monitor and I still get no signal on that port but also noticed it still has my original monitor listed. I noticed in Hackintool it says it is injecting the EDID for that monitor but my only other options are to inject EDID for other Apple displays. I extracted 2 separate EDID files in hex for the smaller monitor, 1 straight to it & a separate one that gets generated when running through the KVM.
Then again I feel that I'm going down the wrong rabbit hole by switching monitors as I believe that something is just disabling this DVI-I port. To confirm that I connected it directly to the TV bypassing the monitor via a DVI-I to VGA cable. My BIOS and first clover screen display, as soon as I select MacOS the TV tells me that the mode is unsupported for a while until I can tell that the GUI has booted and then the TV says that there is no signal.