I already do backup on external HDD and I'm planing to do cloud backup as well.
As I could see, for long-term storage, not readily available (i.e., you have to wait hours to begin the recovery), some storage services are cheaper (AWS, BackBlaze, and so on).
But the storage is done in buckets, and also data transfer (upload and download) is billed.
So I need some backup tool that:
can store files on the cloud
Does incremental backups (to minimize costs of data transfer)
keeps control of files stored in buckets for long term storage
perhaps can deal with the local, external HDD backup.
Bonus for GPL or not proprietary data formats, as I need to be sure that I'll be able to recover the files if necessary without depending on a proprietary software/format to untar/decrypt/unzip my files.