Urbackup_snapshot_helper is broken on TrueNAS (FreeBSD) with ZFS

Anyone here using UrBackup on TrueNAS CORE?

  1. Datasets from old full file backups are not physically deleted by UrBackup even though they no longer show up in the WebUI nor are referred to by the datasets of any incremental file backups that do appear in the WebUI. remove-unknown does not find them. Had to remove them manually with zfs commands.

  2. Deleting raw CoW incremental image backups always fails.
    urbackupsrv -u root remove-unknown prints many errors like this:

2022-09-19 22:23:58: Deleting incremental image backup ( id=24, backuptime=2022-03-25 06:23:24, path=/mnt/mypool/ub01/b/x-PC/220324-2323_Image_C/Image_C_220324-2323.raw, letter=C: ) from client "x-PC" ( id=2 ) ...
2022-09-19 22:23:58: Deleting image backup ( id=24, path=/mnt/mypool/ub01/b/x-PC/220324-2323_Image_C/Image_C_220324-2323.raw ) ...
Checking mypool/ub01/i/x-PC/220324-2323_Image_C for dependencies...
cannot open '-H': dataset does not exist
cannot open '-o': dataset does not exist
cannot open 'value': dataset does not exist
cannot open 'mypool/ub01/i/x-PC/220324-2323_Image_C@ro': dataset does not exist
2022-09-19 22:23:58: Deleting image backup failed.

Running urbackup_snapshot_helper directly prints exactly the same messages.
Command: urbackup_snapshot_helper 1 remove x-PC 220324-2323_Image_C

Tested on TrueNAS 12.0 and 13.0, jail with FreeBSD 12.2 and 12.3

I think that ZFS support is not sufficient tested or implemented.
I have found that remove-unknown command don´t work in ZFS environment, in my case, it deletes all backups from DB (not from disks).
Also I found that when you delete a computer, it doesn´t delete the ZFS dataset that belongs to that computer.
And also the problem with Virtual Subclients that don´t work with ZFS.

I hope that all of those issues are under development or at least are known by Urbackup developers.