It works OK with the monitor connected to the board slot. It won't have optimized acceleration though. When you boot do you hit return at the end of your clover-windows UEFI setting/adjustments? If so before you hit return, change the cord to the vcard output and then hit return. It will black screen boot until you get to password. If its blurry don't worry, just enter your password calmly and hit enter, it should open up into a beautiful view of Sierra. Check your about this Mac and system report for "supported" status and the monitor should show just below the card if you did it right. Run (download if necessary) uningine and post results.
If your not getting "supported" status check to see that the 4000kext took the 67DF1002 ID change. Repeat the change again, following every step of the picture guide and then run kext wiz or kextbeast to lock the changes in. I just had to redo the change to one of my new Gol"d Medal disks, the Sandisk 120 gb. But it took the second time using the method and now I'm running my XFX RX 480 8gb "supported" on it.
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