[proactivesvcs]

I use restic which has very flexible retention policies. Rather than retain simply "x days", one can have it "keep the last x hourlies" all the way up to "keep the last x annuals", and XOR many criteria in one policy. Since it uses snapshotting, compression and deduplication it's very storage-efficient. They also offer a simple REST server which allows one to backup with append-only permissions, which can alleviate a ransomware attack.