kenwsf,
Looked at your config.plist posted above. My comments follow:
1. In Booter/Quirks, you have RebuildAppleMemoryMap Value YES; that should be NO according to both the OpenCore Skylake Guide and my working Skylake computer.
2. In DeviceProperties/Add/PciRoot(0x0/Pci(0x2,0x0)/AAPL,ig-platform-id Value, you have 00001219. It should be 01001219 to run your RX 580. Also you do not need the two frame buffer-patch-xxx items below. You should delete them.
3. In Kernel/Add, the Lilu item which is at item 1 should be moved to item 0 because it needs to be above IntelMausi.kext as well as above all the others.
4. In Kernel/Quirks, you have AppleCpuPmCFGLock Value YES. That should be NO according to both the OpenCore Guide and my working Skylake computer.
4a. For DisableIoMapper, you have value YES. This should be NO if you have already disabled Vt-d in your BIOS, otherwise it should be YES as you have it.
4b. For DisableRtcChecksum, you have Value YES. It should be NO unless you "either receive BIOS reset or are sent into Safe mode after reboot/shutdown" per OpenCore Skylake Guide (my computer uses NO).
4c. You have XhciPortLimit Value YES. It may work for you, but it's better to have a USBPorts.kext in your EFI/OC/Kexts folder enabled in config/Kernel/Add, and have this set to NO.
5. In Misc/Security You have SecureBootModel Value set to Disabled. I use Default, but you can probably use either one.
6. In PlatformInfo, I do not have a "Memory" subsection. Do you need that, and where did it come from?
7. In UEFI/Drivers, you have OpenCanopy.efi enabled, but the necessary setup in Misc/Boot does not match.
If you want to use OpenCanopy, you need to change:
a. Misc/Boot/PickerAttributes Value from 1 to 17
b. Misc/Boot/PickerMode Value from Builtin to External
8. In UEFI/ProtocolOverrides, you have FirmwareVolume Value NO; that should be YES. This is important!
Good Luck!