That's it (My iMac is from 2013). I installed Catalina last night. I had to first create a Mojave partition for an application that the developer is still working on porting to 64 bit. It accesses data on my Catalina partition. So this morning I converted my wife's newer Mac to Catalina. It just finished and it has SideCar. Odd, it didn't change the desktop screen nor offer the quick tutorial, maybe because I copied the installation app from my computer to hers instead of the normal procedure.
I will either be getting a new iMac for Christmas, or half-way paying for, and then finishing it this summer. (if the new iMacs are good upgrades, I would prefer that).