Creating a bootable ISO backup stored on IBM Spectrum Protect
First you need to install systemback
$ sudo apt install systemback
Pictures and illustrations are from https://linuxhint.com/create-iso-current-installation-ubuntu/

After installation, one can start the sytemback application

To create an ISO bootable backup of your system, select the "Live system create" button

Select the mountpoint of where SPFS is mounted as a "Working directory". For example /backup
Give at good name of the system "Name of the Live system"

Click on "Create new" button to start the ISO creation

This might take a while.
Once completed, you have a ISO backup that is bootable on your Spectrum Protect backup server