1)Check if their object store uses v2 and/or v4 signatures, and if v4, does it uses a region settings. It's possible they need to configure the following setting:
The authentication region to use for signing requests when interacting with the remote storage system supporting the S3 API.
Used with v4 signatures only.
If unset and the endpoint (either automatically constructed or explicitly set with remote.s3.endpoint setting) uses an AWS URL
(for example, https://s3-us-west-1.amazonaws.com), the instance attempts
to extract the value from the endpoint URL (for example, "us-west-1"). See the description for the remote.s3.endpoint setting.
If unset and an authentication region cannot be determined, the request will be signed with an empty region value.
2) Managed to o execute splunk rfs command against his Netapp Storagegrid object store, and is able to successfully complete his SmartStore configuration, after adding:
remote.s3.signature_version = v2
Note: "remote.s3.clientCert = " would return null value, which in this case was fine, but same config might work for other Storagegrid env.
indexes.conf stanza for future reference: indexes.conf stanza for future reference: