This is something I’ve wanted for a long time. I opened a ticket with cPanel about it yonks ago as Ceph storage is offered by more than just Amazon, and yet cPanel was making it super hard to use for backups.
Well in the next release of cPanel, this will no longer be the case! If you’re on version 74 (which is in release stage, but not current, so most people do not have it yet) you can do this.
Add A New Backup Option
Go to Home > Backups and open up the settings.
In there, you can add a new Backup option. Pick S3 Compatible:

Configure for DreamObjects
Now just throw in the right data:

You’ll want to use objects-us-east1.dream.io
for the endpoint, and then your bucket and keys.
Back it Up
And with that you’re done. Thank you, cPanel!