If you’re on the Virtualmin 8 repos (which is not indicated by which version of the Virtualmin virtual-server module you have, it depends on when you installed), you should just be able to install it, I think. Something like apt install virtualmin-podman
@Ilia posted about it here when it was first released for beta testing: Welcome the new Virtualmin Podman Plugin
But, I don’t think you need to install it via the non-standard method covered in that first post, anymore. I would guess it’s in the repo.