Current EFI attached for reference, using Clover 5118 and iMac19,1 with iGPU enabled as headless, graphics output using 5700XT card. Generate or copy over your existing serial numbers to the config file, random values exist within.
Native NVRAM needs to be enabled by disabling the BIOS cfg-lock if not already patched, hopefully the beta F12h BIOS has this toggle but I have not installed it to find out.
Disable the iGPU in BIOS if you are having repeated 'no entry' memory allocation errors on startup. This happens very occasionally for me but will boot fine on the next attempt. I have always had iGPU enabled for quick look and rendering compatibility.
CSM Support: Enabled
VT-d: Disabled
Initial Display Output: PCIe 1 Slot
Internal Graphics: Enabled
DVMT Pre-Allocated / Total Gfx Men / Aperture Size: 64M / 256M / 256MB
Audio Controller: Enabled
Above 4G Decoding: Enabled
PCH LAN Controller: Enabled
Wake on LAN: Disabled
IOAPIC 24-119 Entries: Enabled
Legacy USB Support: Disabled
XHCI Hand-off: Enabled
USB Mass Storage Driver Support: Enabled
Port 60/64 Emulation: Disabled
Network Stack: Disabled
LEDs in System Power on State: On
LEDs in Sleep, Hibernation and Soft Off States: Off
PTT: Disabled
SGX: Disabled
3DMark01 Enhancement: Disabled
Platform Power Management: Disabled
AC Back: Always Off
ErP: Disabled
Soft-Off by PWR-BTTN: Delay 4sec.
Resume by Alarm: Disabled
Power Loading: Auto
CEC 2019 Ready: Disabled
RC6(Render Standby): Enabled
XMP Profile 1
Hope that helps