From OS Monterey to an older OS version, or how to uninstall OS Monterey to install High Sierra

Nazaren wrote:

I own a Macbook air 13" early 2015,

I upgraded to Monterey and I am not happy at all and would like to go back to an OS older verison High Sierra, Catalina or others, how can I do the downgrade. I downloaded the High Sierra dmg files, but the High Sierra installer is too old for the OS Monterey?

How can I uninstall the OS Monterey without loosing data, is there an easy option to install

f.e. High Sierra.

You need an adequate backup— because in effect you have to delete everything and start a new.

Import your user data from backup

same as here—Revert your Mac to a previous macOS version
https://support.apple.com/en-lamr/guide/mac-help/mh15216/10.15/mac/10.15

Erase and reinstall macOS - Apple Support - https://support.apple.com/guide/mac-help/erase-and-reinstall-macos-mh27903/mac

The older macOS installer backups on this server:

https://support.apple.com/en-us/HT211683

verify you are using the Safari browser to download/initiate the macOS links.

Can you tell us what about Monterey you're not liking? Maybe we can offer fixes to problems or workarounds that would make Monterey more to your liking. It would be easier to fix problems than to roll back to an earlier system.

Have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

If you do roll back you do have a current backup of your boot drive from before you upgraded to Monterey, right?

As noted, you will need to first erase your HD to install an older operating system, so unless you first backup all your files they will be lost. Since you are going to move on to install Linux Ubuntu, it will be irrelevant.

You may also want to have a look at How to create a bootable installer for macOS. BTW, 32-bit applications are no longer supported starting with macOS Catalina.

- Pie Lover