I went with this official updated guide
https://dortania.github.io/OpenCore-Install-Guide/
I first tested it on my current Catalina installation (created the OC USB), it went great, booted right away, then I just copied the USB EFI to my SSD EFI and never looked back. Then I just updated to Big Sur. No need to go clean. However, it helps if you have a vanilla hack, so all kexts in EFI. Just go with the guide, not leaving out any step. Create the USB, try it. I copied my SSID and other IDs from clover to OC.