What's happening?

Navigate to DeviceProperties -> Add .

Use or iMacPro1,1 – these rely on dGPU. Do not use iMac19,1/20,1 – they expect full iGPU acceleration.

If not configured correctly, you may see only 7MB or 14MB of VRAM and no hardware acceleration.

The absolute best way to run a Hackintosh on a modern Intel system is to disable the UHD 770 in macOS and use a native AMD Radeon graphics card instead.