Have a look at restic for a good alternative to this.
Two scripts linked at the bottom of README.md are almost perfect and I used one or another for years, but one of them sometimes misses to hard link with previous backup, creating new full backup and wasting resources -- not something that's easy to detect since they all look correct before 'du' or similar analysis.
saf solves few of the problems I faced during the years in a elegant way: multiple targets, target related commands, reliability. Why not XY? Why not saf?
This is a backup tool, not a security one. The fact that the author does not understand this is a real problem and a red flag.