Thank you, feartech!
From post 2 “If you're using the AMD RX and Vega graphics cards, you will need to set the Devices/Graphics/RadeonDeInit=No flag in /Volumes/EFI/EFI/CLOVER/config.plist.”
I can’t find “Devices/Graphics/RadeonDeInit=No flag” in the config, plist.
I am “using the iMac18,3...