OK, so I went off on a complete tangent, looking at your User Profile system (x58A-UD3R) and not your MSI Z390-A system. You can obviously ignore the information regarding your X58A-UD3R system in my post above, unless you want to upgrade that system from Mavericks to a newer version of macOS.
It always helps when you put the system you want help with in your User Profile, that way we know which system you are looking for help on. Without having to read through the whole thread to understand which system is being problematic.
Anyway, here is an OpenCore EFI for a Coffee Lake system running macOS High Sierra, using an Nvidia GPU with the Nvidia Web Drivers installed.
It is based on OpenCore 0.8.7.
- Requires you to add the SMBIOS (serial Number, MLB, ROM and SystemUUID) data for an iMac18,3 to complete the setup.
NVIDIA GPU.
- It contains the nvda_drv_vrl=1 boot argument, which is used for enabling Nvidia's Web Drivers on Maxwell and Pascal cards when running Sierra and High Sierra.
- If you don't have High Sierra or the Nvidia Web Drivers installed, yet.
- Then the nvda_drv_vrl=1 boot argument may need to be changed.
- That being the case, you would need to replace nvda_drv_vrl=1 with nv_disable=1 boot argument, which disables the Nvidia Web Drivers in macOS.
- The nv_disable=1 boot argument is used so your system boots and runs the OS installation without graphics acceleration, i.e. in VESA mode.
- When you boot in to High Sierra you will need to update the OS to the latest release, as the High Sierra 10.13.6 download does not include all the Security updates Apple have released over the years for this OS.
- I would recommend keeping nv_disable=1 boot argument in place until you have completed all the High Sierra updates, there are a few if I recall correctly.
- Once macOS says your system is up to date then and only then should you install the Nvidia Web Drivers. I say this because each High Sierra update has its own release of the Nvidia Web Drivers. I am sure you don't want to waste your time downloading and installing a dozen releases of the Nvidia Web Drivers.
Everything else should be kept as I have configured the EFI folder.
After adding the SMBIOS data to the OC config.plist do the following.
- Copy the OC EFI Folder to a spare USB pen drive's EFI partition.
- Boot your Coffee Lake system from the USB, you need to press the F11 key on an MSI board IIRC.
- Make sure you use the ResetNvramEntry.efi from the OC boot screen.
- The ResetNvramEntry.efi will not be visible, but all you need to do is press the spacebar to display the hidden icons while on the boot screen (should be the OC GUI not picker list).
- The system should automatically reboot after you have selected the ResetNvramEntry option (pressed Enter with the ResetNvramEntry highlighted).
- Reboot from the USB pen drive again, this time select your High Sierra boot or installation icon.
Hopefully the system will boot in to High Sierra or the installer with no issues.
If you get a kernel panic, take a photo of the verbose text shown on your screen and post a copy here.