Veeam Backup - Backup and restore VMware and Hyper-V virtual machines with Veeam Backup Free Edition. Unlimited hosts and VMs. Free forever.
Restic - Easy: Doing backups should be a frictionless process, otherwise you are tempted to skip it.
Zerto - Virtual replication & recovery solution
Duplicati - Free backup software to store backups online with strong encryption. Works with FTP, SSH, WebDAV, OneDrive, Amazon S3, Google Drive and many others.
Acronis Backup and Recovery - Acronis Backup is a data recovery solution that offers more ways of storing and recovering drives, folders and files as compared to other similar solutions.
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.