Can i change the operating system on a brand new mac?

What does softwareupdate via the Terminal output in you Mac mini?

Maybe you could make a Big Sur bootable installer and try to Option-boot it -- if it boots then it might well install it (my Mac mini boots such Mojave installer but fails to boot High Sierra installer).

My Mac mini 2018 has the following output:

softwareupdate --list-full-installers
Finding available software
Software Update found the following full installers:
* Title: macOS Monterey, Version: 12.1, Size: 12157035487K
* Title: macOS Monterey, Version: 12.0.1, Size: 12128428704K
* Title: macOS Big Sur, Version: 11.6.2, Size: 12433351292K
* Title: macOS Big Sur, Version: 11.6.1, Size: 12428472512K
* Title: macOS Big Sur, Version: 11.6, Size: 12428553042K
* Title: macOS Big Sur, Version: 11.5.2, Size: 12440916552K
* Title: macOS Catalina, Version: 10.15.7, Size: 8248985973K
* Title: macOS Catalina, Version: 10.15.7, Size: 8248854894K
* Title: macOS Catalina, Version: 10.15.6, Size: 8248781171K
* Title: macOS Mojave, Version: 10.14.6, Size: 6038419486K

Then I can download the latest Big Sur:

softwareupdate --fetch-full-installer --full-installer-version 11.6.2

And make a bootable installer from that:

https://support.apple.com/en-us/HT201372

Hi Josephus87,

It depends. The general rule is that you can't downgrade from the macOS version that shipped with the Mac. In reality (AFAIK), you can't downgrade past the version of macOS that originally shipped with that Mac model.

For example, I recently got a refurbished M1 MacBook Air from Apple that shipped (to me) with macOS Big Sur 11.6. However, I was able to successfully downgrade to macOS Big Sur 11.0.1, because the M1 MacBook Air first shipped with that version when it was released. The same should be possible with the M1 Mac mini and M1 13" MacBook Pro.

The M1 iMac (AFAIK) shipped with macOS Big Sur 11.3 or 11.4, and the 14" and 16" MacBook Pros shipped with macOS Monterey.

If you still want to downgrade your Mac mini to macOS Big Sur, please provide the following info and I'll post the best steps for the downgrade (if it is possible):

• Year and model
• The chip or processor inside

You should also consider that the latest macOS version is generally the safest to use online. Major new macOS versions typically contain security enhancements and fix vulnerabilities that never get fixed for the previous macOS versions.

No, I'm sorry you can't. Any Mac will accept only the operating system it shipped with or any later release, not an earlier OS.

if it's not an apple m1 cpu you maybe able to install the older version in a virtual machine in parallels