Restic is fantastic. It’s just one binary, has support for various cloud services (including Backblaze which I use as well), snapshots which can be mounted with FUSE. It’s really quite useful. Borg I believe is similar?
Either way, I feel like today there is no reason to use awkward rsync solutions when better tools are out that have proven themselves.
It is always the worst code you wrote that survives. There’s a terrible university dorm management software I wrote eight years ago as a student. They still use it. The crazy complicated test framework wrappers for some hardware I wrote five years ago. They still use it. The godawful and crazy complicated communication protocol I whipped up four years ago, still used in medical equipment today.