How do I modify the “S3-compatible server hostname” so that I can use DreamObjects (DreamHost’s Amazon S3 protocol storage)? And are there other settings?
If a provider is using an S3 compatible service, then Virtualmin’s S3 backups should work with it. However, you’d need to get the details you mentioned from the provider. They’d be able to give you the hostname to use, as well as the bucket and key.
It looks like the details for configuring that were recently moved… that can now be configured in Backup and Restore -> Cloud Storage Providers -> Amazon S3.