Because it is a Linux distribution, there should be tools that already let you produce an encrypted backup file. Even if there were not a GUI, I know of some common command line utilities that should work. I expect that it would be sufficient to just backup the /home/purism directory. I am not sure what is stored outside of /home/purism. Probably WiFi access point credentials and a few minor things, like system settings/preferences. You could backup every file, but that might confuse something in the operating system if restoring on top of different versions / settings. If I wanted to do a full system backup, I would use the dd tool to capture the entire internal storage and compress and encrypt it to a USB drive. Restoring it might be challenging unless you can boot from USB or SD: Librem5 sd and boot order - #22 by dos