For Kasten K10 to work with Longhorn properly, you have to create a volumesnapshotclass.
Annotations for Kasten K10 must be set as below:
kind: VolumeSnapshotClass
apiVersion: snapshot.storage.k8s.io/v1
metadata:
name: longhorn-snapshot-vsc
annotations:
k10.kasten.io/is-snapshot-class: "true"
driver: driver.longhorn.io
deletionPolicy: Delete
parameters:
type: snap