How do I downgrade my the OS on my MacBook Air?
I want to downgrade my OS system back to Catalina. How do I do this?
Question marked as
It will be very helpful to include your device model year..
Catalina was introduced in 2019..
If your device is model after 2019 (such as late 2020) -- then you likely out of luck.
OK, got this out of the way -- the best bet will be "download Catalina" from Apple website.
Note: it will be much easier to use prior 2020 machine for the download.
Create a bootable installer for macOS - Apple Support
Make a USB boot drive.
The article above is quite detailed yet long.. read it through first.
AND
"Backup" the data..
Since you will be backward downgrade the OS, the TimeMachine sometime does not like it/will not let you go through. Make sure you have TimeMachine and direct files backup, just in case.
Best.