Download Mojave late 2020

Need to download Mojave 

Situation:

Currently (Dec.  2020) my Mac Mini (late 2012) is running High Sierra 10.13.6.  The 2020 version of TurboTax will not operate on OS 13 and needs Mojave 10.14 or newer.  I am also still using Quicken 2007 that supposedly will not operate on Catalina or newer OS from Mac.  There may be some other older software I am using that is 32 bit based that will not function on OS 10.15.

I need to get Mojave that is the intermediate OS between 32 bit and 64 bit systems.  I would like to do a slow transition of hardware and software over the next year since it is not a cheap or trouble free step.  I am not young and technically sophisticated, although when I was I bought the first Mac introduced in 1984. So I am looking for something straight forward.

Question: 

How do I download a copy of Mojave or take some other route to get my 2020 TruboTax and Quicken 2007 to continue working for the next year while I transition to newer hardware and software?  I have looked through the common searches and checked out the following two websites that are supposed to download Mojave:

https://support.apple.com/en-us/HT210190

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

I click on the link that takes me to the Apple Apps site and click on the Mojave open button and get this popup message:

This copy of the Install macOS Mojave application is damaged, and can‘t be used to install macOS.

I have use Mojave as search term for Mac Mini files and trashed an installer for Mojave that was in the applications folder then emptied the trash.  I did not come up with any anything else remotely related to an older version or installer. On retry at the above websites same message came after a download installer was installed and I tried to open it.

What should I do to at this point to get Mojave?