Downgrade from Monterey to El Capitan
Hi everyone, I'm at my wits end here and need help if anyone can?
I won't explain the catalogue of disasters that led me to upgrade my perfectly stable Mac Pro (late 2013) running macOS 10.11.6 to Monterey 12.6 but suffice to say it was AVID's fault. Long story short, I need to revert to 10.11.6 from 12.6.
I have read several articles about how to do this but there is fundamental information missing in every one of them so far.
First of all I restarted in recovery mode and tried to restore from a time machine backup from 3 days ago.
My backups are on an external drive, formatted in HFS+. The MacPro has a 256Gb SSD formatted in APFS. Can't restore from Backup (crazy, right?)
"The system can't be restored onto this disk because HFS systems can't be restored to space sharing APFS volumes. Reinstall macOS on this disk and then use Migration Assistant to transfer data from your backup instead" (What is the point in a backup system that you can't restore from?)
So, I follow the instructions, go and buy a USB pen drive, download the El Capitan installer and make a bootable drive out of the pen drive.
Restart MacPro from the Pen Drive, holding the Alt button, and get to the Startup Manager window.
If I choose "reinstall system", the MacPro SSD does not appear as an option as to where to install it.
If I choose "Restore from Backup" No destination disks appear at all.
If I choose "Disk Utility" no Macintosh HD or Data appears, only the generic, APFS formatted "APPLE SSD SM0256G Media" drive. If go to erase it, it does not give me the option to format it in APFS.
So it appears that I can't erase my MacPro SSD and format it as APFS.
It appears that I cannot install macOS 10.11.6 on the disk from the "bootable" drive.
It appears that I cannot restore from my backups.
Does anyone know what to do???
Thanks in advance.
Mac Pro, macOS 12.6