Hi Steve,
This is a valid workaround for using it with AutoCAD 2020. The hardest part is just getting the installer to run. If you have a version pre 2020 the installer should work just fine and then you can open AutoCAD 2020 and netload the plugin.
If you need to deploy it across machines that only have 2020, you will first need to download it to a machine that has a pre 2020 AutoCAD, copy the installed files and place them on the 2020 machines. You will then be able to netload the plugin using the ArcGISForAutoCAD.dll.