Attached OpenCore 0.7.7 EFI for my computer at left with blank Generic data in the config.plist/Platforminfo/Generic section. You fill in. Also with the following changes: I use a dGPU (RX580), so I edited this EFI to change config.plist/DeviceProperties/Add/second item to an appropriate argument "07009B3E" for an Intel integrated graphics processor. If it does not work, try instead "00009B3E". Numbers are from the Guide.
[Edit, hang on, I made an error...] ... okay, fixed. I left my SMBIOS (iMac19,1) in place, but you have an 17 8700 and maybe you will need iMac18,3; not sure.