Legacy-Kexts VS OcBinaryData

Try adding SATA-unsupported https://github.com/khronokernel/Legacy-Kexts/blob/master/Injectors/Zip/SATA-unsupported.kext.zip

I would guess SATAUnsupported.kext, but you should check here and make sure you've disabled anything unsupported, such as IRRT, hardware, etc. Again, I have no idea what your hardware and OC configs look like. Maybe start fresh, and open a new thread? You mentioned using the same files for your Clover and OC configs, and can personally tell you this rarely works right.

SATA-unsupported

For Catalina, You should use this kext instead SATA-Unsupported(opens new window)

Thanks for the tip, I tried installing SATA-unsupported.kext and AHCIPortInjector.kext

ATAPortInjector

I took a look at your EFI, and I don't see any obvious errors in the config.plist. Concerning the ACPI, I don't think a valid EC is required in macOS prior to Catalina 10.15; thus, SSDT-EC is unnecessary. Concerning the Drivers, I don't think Ps2KeyboardDxe is required. Also, why use VBoxHfs-32 instead of HfsPlus32? I am curious as to where you got most of your kexts; USBInjectAll only works on El Capitan 10.11 and above, and I don't think IOATAFamily nor SATA-unsupported are required for your laptop; does your laptop even support AHCI or SATA?. AHCIPortInjector and VoodooHDA, I'm not sure about (for the latter, I think you should be using VoodooHDA-FAT). The others look fine, though.

HfsPlus.efi is missing, get that from this link and then put it in your Drivers folder: https://github.com/acidanthera/OcBinaryData/blob/master/Drivers/HfsPlus.efi

Fixed loading macOS with legacy boot without Apple Secure Boot: there is a new PE (Portable Executable) loader that broke legacy boot, blocking the loading of legacy drivers as HfsPlusLegacy and preventing OpenCore from booting on legacy systems when Apple Secure Boot is disabled. With this fix, legacy boot can work with or without Apple Secure Boot. This issue was detected after version 0.8.8 was released. While you are on 0.8.8, you must download the new versions of the drivers HfsPlusLegacy and ExFatDxeLegacy (the one/s that are necessary), available in Acidanthera. This is not required if you are on OpenCore 0.8.9.

Update Resources as well: https://github.com/acidanthera/OcBinaryData

Check if you have the latest resources Folder (included in OC Binary Data)

Copied from the latest OcBinaryData

I'm able to download and open up the zip as instructed, but as far as dropping the "ExFatDxeLegacy.efi" file into the right location on my ESP (which I understand to be my boot drive, where OCLP was originally installed), I'm at a total loss.

Have you tried downloading the version from https://github.com/acidanthera/OcBinaryData ?