From snapd 2.57+, snaps can save small amounts of persistent data to the ubuntu-save partition.
This maybe should point to the SNAP_SAVE_DATA documentation for snaps.
This data will survive a factory reset. Device provisioning needs to consider space requirements and snap developers need to understand the consequences of storing persistent data to ubuntu-save …
This maybe should b expanded:
As it survives factory-reset it is recommended for storing device-oriented data and not data belonging to a particular user of the device.