Veeam Backup is, in my opinion, one of the best free backup solutions available. The Linux version particularly shines with its ability to create snapshot backups of Ext4 partitions.

Unfortunately, the Linux version has a major drawback compared to its Windows counterpart: backup scheduling is extremely limited. You can only specify the day and hour for when backups should run. If the computer is asleep or powered off at that time, the backup won’t execute and, more importantly, won’t be rescheduled.