The table in the following document mentions that block storage is "Configurable" for Loki Logging, but in the LokiStack CR, options other than S3 cannot be configured directly. Block storage should be "Not configurable" (even if it can be configured via ODF)

https://docs.openshift.com/container-platform/4.13/scalability_and_performance/optimization/optimizing-storage.html#recommended-configurable-storage-technology_persistent-storage