To restore my Mac's original OS (High Sierra), I used Mint. This was written to a separate sata SSD drive using a bootable USB drive created with Mint. All went smoothly and High Sierra appeared to be normal until it was restarted with this message appearing in the upper right of main screen: "Incompatible Disk, This Disk uses features that are not supported on the version of macOS". And that's the good news. The bad news is that two other sata SSD drives containing OCLP installed Monterrey and Big Sur no longer boot. When starting each, I get this message together with the Apple logo: "supportt.apple/MAC/Startup". Is there any fix for this or must I re-install these other operating systems? Moreover, is there any other means to install High Sierra without corrupting the other drives?
Your input would be appreciated.
Your input would be appreciated.