Our policy is to only support consumer-targeted cloud services (i.e. Google Drive but not Google Cloud Storage, OneDrive but not Azure Storage, etc).
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Déjà Dup used to offer several more-technical cloud storage services. As of version 35.4, it no longer shows those services by default because in the long term, we’d like to move away from them.
Specifically, the following services are deprecated: Amazon S3, Google Cloud Storage, Openstack Swift, and Rackspace Cloud Files.
How to Enable Anyway
If you want to restore from one, simply start a restore and select it from the location drop down. If you want to back up to one, open dconf-editor and navigate to /org/gnome/deja-dup and change the backend key to either gcs, openstack, rackspace, or s3.
When you next open Déjà Dup, you can now see a new option in the storage location drop down.