Here’s the sources for the various available bundles in Virtualmin-Config: Virtualmin-Config/lib/Virtualmin/Config at master · virtualmin/Virtualmin-Config · GitHub (--minimal flag triggers either MiniLAMP or MiniLEMP).
On Debian/Ubuntu you’ll have one of the four possible stack packages, so you can do something like:
# dpkg -l |grep virtualmin*stack*
Which will return something like virtualmin-lamp-stack or virtualmin-lamp-stack-minimal.
On CentOS, we use yum groups so you can use yum grouplist |grep Virtualmin to see which stack group is installed. (And Virtualmin Core is always installed, as it is the core Webmin+Virtualmin modules packages that are always needed.)