Arq.app can backup external disks to most of the big cloud storage providers really well. Unlike Backblaze, they don’t delete these backups if you don’t connect your drive for a specific amount of time.
I’ve used Arq to backup about 2TB of external drives to AWS Glacier. It even let me set the encryption key for the data myself!
I used to backup with Arq to S3 and the restores were very fast. With Glacier, Arq initiates the data retrieval and waits for file availability in the UI. Glacier can take a day or so, laptop needs to be open and connected to internet during the time for the transfer to complete. Given I'm primarily backing up external drives, I find this UX not an issue, but if you wanted backups with instant accessibility, backing up to S3 really isn't that pricy.
I’ve used Arq to backup about 2TB of external drives to AWS Glacier. It even let me set the encryption key for the data myself!