I use Borg to back up. It is available for many operating systems, including macOS and Linux. Well documented, there are even scripts to back up your data automatically. I use this archiver and I am very pleased with it. Its main feature is that each new backup will only contain information that has changed against the previous backup. This saves time and space in backup storage. You can create and manage your own backups, or modify the documentation automation scripts for your needs, or write your own. I use two external USB drives and a modified automation script, and this solution suits me perfectly.
For a macOS and Linux compatible file system, see UDF: