Hello, I have a very basic question and would appreciate a pointer in this regard. If we are spinning up k8s clusters (not baremetal) on Harvester, is there a straightforward way to configure the Harvester provided Longhorn as the storage class for those k8s clusters? What is the Longhorn endpoint to be used with the Longhorn CSI?

I don't use it, but I think this is what you're looking for: https://docs.harvesterhci.io/v1.6/rancher/csi-driver#passthrough-custom-storageclass

Make sure to set the "Cloud Provider" to "Harvester" while provisioning the cluster. It's the default, so probably you did this already. After cluster provisioning was successful, you'll find a storage class with the name "harvester" in your guest cluster where you can provision (only) RWO volumes. This storage class is using Longhorn in the background.

rwx volumes on guest only work with storage network: https://docs.harvesterhci.io/v1.6/rancher/csi-driver/#rwx-volumes-support