That sounds like a good idea, but the process you describe doesn't work. I type "macos monterey" in the App Store search window, and I get a variety of things that seem entirely unrelated to that OS. Virtual Machines Hub? Small Business Pack? Day & Night World Map Studio? Why don't I see the Monterey OS? In fact, the same thing happens if I search for other Mac operating systems there. What in the world is wrong with Search in the App Store?
So, I had to go to
https://apps.apple.com/us/app/macos-monterey/id1576738294?mt=12 and select "View in Mac App Store". That gets me to MacOS Monterey in the App Store. Bizarre.
Now, when I click "Get" there it flips me into Software Update which, as I said, doesn't work. Now, cntl-Get does it for me. It kicks off Software Update and downloads the operating system. It then asks if I want to install it, and asks for my password to "Unlock". I enter my password, and it just keeps asking.
Yes, the install package was downloaded into my applications folder. I click on that, and I just get asked for my password again. I can't start the installation manually.
So I tried creating another Administrator account as you suggested. I called it "test". Logged in as "test" and went to Software Update and tried to update. It asked for passwords again, but only allowed me to enter a password from my account and the real Admin account, neither of which worked. It did not allow me to update as "test".
Not sure how it can be an ownership problem as my passwords work for everything else. It's a Software Update problem.
I'm screwed.