Not OP, but I have been using borg backup [1] against Hetzner Storage Box [2]
Borg backup is a good tool in my opinion and has everything that I need (deduplication, compression, mountable snapshot.
Hetzner Storage Box is nothing fancy but good enough for a backup and is sensibly cheaper for the alternatives (I pay about 10 eur/month for 5TB of storage)
Before that I was using s3cmd [3] to backup on a S3 bucket.
This is quite a bit more expensive than Backblaze if you have more than 5 TBs or so
I cannot edit any longer, the second link was supposed to be
[2] https://www.hetzner.com/storage/storage-box/