Testing office-js addins against old versions of excel

I'm developing an office-js addin for corporate client which insists on using legacy versions of Excel (1708 or 1808).

But when I install excel from office 365, I get version 1906.

In the old days, with software, there were installers you could find in a directory that had version stamps on them, and you could create a VM, and just install the version you wanted. But the fancier installers appear to download stuff automatically and always (at least default to) the latest versions.

How do I install a legacy version of Excel on a VM for testing?