Hi,
I did setup the last version on Ubuntu (and also tried a Docker app) of Cloudberry backup. While creating a backup plan to Azure (or even to local directory), I cannot select files too backup as the object "Specify files & folders you want to backup" is showing blank.
So, to conclude this: the reason is that CloudBerry Backup for Linux does not support ZFS for source (and most likely, for destination too).
Ext 2/3/4 are supported and so is BtrFS, that's what we recommend using.