I'm desperately try to change my operating system back as my old machine really can't cope with Catalina. Far too slow. I've rebooted using command,/shift etc.. I get the mountain lion os picture and a box to enter the drive that mountain lion is located. Unfortunately no options are shown and I can go no further.
Any ideas gratefully received
Jeff
It helps if you were to provide the exact model of your Mac, the kind of drive (HD, Fusion, or SSD), and any other off-standard feature installed. Downgrading is probably one of the most harrowing procedures you can make, unless you are content with erasing everything on your drive, including all third-party apps, personal data, and settings, unless you have a comprehensive backup of all your data.
Have you tried rebooting into Safe Mode to see if the Mac runs any better, or tried reinstalling Catalina? Maybe, hopefully, it was just a failed installation that is causing this problem.
