How to downgrade to Catalina 10.15.5
Catalina 10.15.6 fatally broke my VirtualBox setup. Unpredictable and random crashing. I am lead to believe that the cause is a kernel memory leak (source VirtualBox & VmWare forum postings).
I want to downgrade to Catalina 10.15.5 which was working fine.
According to Apple support I have to erase my system, install a new copy of Mojave followed by Catalina 10.15.5
The last part of that does not work. Catalina 10.15.5 from the App Store Catalina page 10.15 first but 10.15 is not on the App Store.
Apple support helpfully pointed out that Big Sur will be out soon that Big Sur will not run on my iMac (according to pre release documentation)
Can anyone advise me how to get Catalina 10.15.5 installed.
For clarity I do not want 10.15.6 the current release.
iMac 21.5″, macOS 10.14