Catalina - Screen Tearing After Boot

iMac15,1 - i7 4770 3.4 GHz, 16GB RAM, EX 570 8GB (DVI only)

I have a Dell 9020 that I have modified to work with Mac OS. I upgraded the power supply and purchased a PowerColor Radeon RX 570 8GB, but it only has a DVI port. I realize this is not ideal, it works for me for the time being (if it would work . . .) but I can sell and rebuy, if that is the ideal solution.

Anyways, when I try and boot with the 570 installed, it turns on, I see the Clover boot screen, and then when it tries to boot to OS the monitor screen flickers until I shut it down.

This is my EFI folder from my USB: https://imgur.com/WOFE6Oj

I have Clover configurator installed on the OS hard drive, but I can't find the EFI folder on the disk? I probably have missed something along the way and that is causing my issues. It does not seem to want to boot without the USB drive plugged in so I've obviously missed a step (or two) along the way.

Thanks!