This seems to imply that the loki instance must be running on Google cloud as well - no auth, no secretKey passed, just a GCS Bucket name given to loki.
Any of the Loki stores can be used it doesn’t have to be GCS (S3, filessystem, Azure etc are also all valid options)
Credentials aren’t provided for the GCS store because the google client we use doesn’t accept them via config, only via environment variables.