+1 for rsync. Have used them for a couple of years. I set up a script to backup my stuff there a couple of times a day. Their daily snapshots have also saved me from my own mistakes on several occasions.

This is the first time I hear about Jottacloud and I'm pleasantly surprised. Their combination of bucket-like storage + mobile app + web app + rclone support seems to tick all the boxes for a Google Drive replacement.

Dropbox’s omission is interesting. I’m using a large paid account to backup a few TB of data spanning many years. Is there something I should know? Losing it would be devastating.

Dropbox is an American company. Most hackers does not trust American hosting companies because of the NSA leaks confirming everyones paranoia. I wouldn't trust Dropbox with a ten foot pole.

I don't think Dropbox is a backup service per se.

Dropbox offers a backup[1] service and has since, I believe, last year.

[1]: https://dropbox.com/backup