Now I get your point, sorry. You can use both Timeshift and BackInTime as snapshot tools, but also configure them to create snapshots on a different drive, making it an actual backup.
I for example use Timeshift in Rsync mode for that reason even though I’m also using Btrfs, which Timeshift supports, but only for non-backup snapshots.
Sorry for the confusion, I guess when suggesting both those tools one always has to specify that you need to save snapshots on a secondary drive for it to be a backup.