ALSO = GPU: Sapphire RX580 Nitro+ 8GB,

Crucial Ballistix Elite 32 GB (4 x 8 GB) DDR4-3600 CL16

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Everything works - sleep, audio, Apple ID, etc. Dual monitors (HDMI and DVI)

Followed the original, now "Dortania," OpenCore Desktop Guide completely. Use the Sanity Checker when you think you've finished working on your config.plist ! Seriously!

There is a big gotcha I discovered after I installed Win10, which was installed on a separate SSD, after I installed Catalina on a Western Digital Blue 1 TB M.2-2280 on the second M2 slot (this board does not like this M.2 stick in the first M2 slot).

Your onboard Intel I211AT network chipset will not load if you have downlevel BIOS and the "Above 4G memory/Crypto Currency mining" in BIOS set to Enabled. You can immediately tell on the Windows login screen because the world icon in the lower right shows disabled (no connectivity). However, if you set the 4G memory to disabled, Catalina will stop loading at the PCI subsystem section, locking up your computer. You can set 4G to enabled but you have to set your boot system to CSM instead of UEFI to get both OSes running - you just don't get the EFI features on Windows 10.

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So I experimented and found a working solution that gets me everything [Warning: YMMV - if you have even a slightly different hardware build than me.] Follow these steps:

1. Please, please, please! Read through the OpenCore Desktop Guide first and walk yourself through it before committing to build. It sounds boring but trust me, you do not want to be halfway through a build, stop to look something up, then forget where you are in the process.
2. On the MSI support site, look for BETA BIOS 7B78V2E2. It is another slim BIOS intended to save space (when going to a higher Ryzen CPU). It has all the features just not the flash --- er, pizazz of the original BIOS screens. Update the BIOS now through M-Flash.
3. Within the BIOS, most of your previous settings may have been reset, change the following:Advanced\PCI Subsystem Settings :: Above 4G memory = DISABLED.Advanced\Integrated Peripherals :: Network Stack = ENABLED.USB Configuration :: EHCI/XHCI Hand-off = ENABLED.Windows OS Configuration :: Boot Mode Select = UEFI.
4. [I installed Catalina before Win10] Follow the Zen section of the OpenCore Desktop Guide for creating the config.plist completely with this one exception:In the NVRAM section, of the "7C436110-AB2A-4BBB-A880-FE41995C9F82" (System Integrity Protection bitmask) key, enter these string variables to the "boot-args" subkey:-v debug=0x100 keepsyms=1 alcid=1 npci=0x2000This string will run the MacOS startup in verbose mode, disables watchdog mode, print symbols as well as text, and finally - disables some of the PCI debugging instructions. THIS IS USED INSTEAD OF SETTING THE "ABOVE 4G MEMORY..." OPTION IN BIOS.
5. I used SmallTreeIntel82576 kext for the onboard Intel I211AT Ethernet chipset. It works and has not failed with heavy two-way traffic.
6. You will most likely get a black screen or forever spinning wheel on the first run. I just removed the USB installation stick, rebooted, and everything sorted out. Additionally, I had unplug and plug back in the HDMI monitor to get Catalina to recognize the second monitor.
7. Install Windows 10 on another drive and use GPT instead of MBR.
8. Back in MSI BIOS set the UEFI boot selection to the MacOS EFI volume. It should give you Windows 10 as the first selection and Catalina as the second in that OpenCore EFI boot manager automatically. Now, you do not need to switch back and forth from CSM to UEFI in BIOS to get one or the other working.QUESTION: Has anyone worked on OpenCore's boot manager to make it a graphical user interface instead of just text? I don't want to monkey around with a wholly different boot manager (I tried rEFIt but Catalina blocks it because it's not 32-bit? Something to that effect.) Thanks.

Sorry for the long post on a success story. I can break this up into a Success story and the longer part into an info guide, if the admins would like.

Catalina using OpenCore 0.5.7

Windows 10 with EFI enabled, Above 4G memory BIOS selection disabled

The kexts used in my build

Pictures: Catalina, Windows 10, my selection of kexts used in this build.

tl;dr

Following the guide worked except that I had to disable PCI debugging at Catalina startup to ensure that I can use the onboard Intel NIC in EFI mode in Windows 10.