Where to find installer DMG for Monterey

Apple does not offer a DMG for Monterey it only offers a Full Self Contained Application called " Install Monterey ".

If the present computer is a Computer Qualify for the Monterey upgrade , one can used these Terminal Command without Quotation Marks to download the Full Version of Monterey.

" softwareupdate --list-full-installers "

Then >>

" softwareupdate --fetch-full-installer --full-installer-version 12.2.1 "

This will download the Full Version placing in Applications Folder the " Install Monterey " though, it will not launch.

Then >>>

 Bootable Installer.  and follow the instruction for Monterey

I was previously able to create a bootable installer for Monterey 12.0.1 using an optical disc (see https://discussions.apple.com/thread/253320087). Originally, I thought that I had to use a prior version of macOS. However, I believe that the method will work with Big Sur and Monterey as long as the Disk Utility is granted "Full Disk Access".

Sometimes a new macOS version does not show u in Software Update especially months after the version has been released. In that case go the App store and search for macOS Monterey.

Apple’s instructions

How to create a bootable installer for macO

System Preferences > Software Update.

It should be offered at the bottom provided that your Mac can upgrade to it.

Or you can find a link at the top of Apple's Monterey web page, which will open Software Update. That web page has a list of the Macs which can support Monterey.

Regarding the iso file, read lllaass's comment in this thread.