Restic - Easy: Doing backups should be a frictionless process, otherwise you are tempted to skip it.

bup - Very efficient backup system based on the git packfile format, providing fast incremental saves and...

Duplicati - Free backup software to store backups online with strong encryption. Works with FTP, SSH, WebDAV, OneDrive, Amazon S3, Google Drive and many others.

rsync - rsync is a file transfer program for Unix systems. rsync uses the "rsync algorithm" which provides a very fast method for bringing remote files into sync.

Snebu - Snebu -- Simple Network Backup Utility

UrBackup - UrBackup is a open source client/server backup system, that through a combination of image and file...