I've been using OpenCore for a while and it works great, so far. If someone wants to try it, they can. At their own risk. Perhaps CaseySJ and some other users want to test it, maybe they are already testing it. Idk.
I've uploaded a my ready EFI folder with OpenCore. It includes the SSDTs by Casey. It works for me, however my config is slightly different with iMac Pro 1,1 SMBIOS. The config in the folder got iMac 19,1 SMBIOS.
This can be tried with USB, or directly with the Mac drive's EFI partition, by adding the "boot" and the "OC" file in the EFI. I'd suggest to not replace Clover with OpenCore, and keeping Clover safe.
Once you boot to OpenCore. You use the numeric keys to boot, I.e 1..2..3.
Important to keep in mind that OpenCore is in its testing times. The purpose by the developers who started this project, was to have a close experience of how Apple booting is.