How to compress and prevent vdi from "ballooning" after each update & deleting large files?

Duplicate of Automate recovering free space from VDI disks?

Citation required.

Automate recovering free space from VDI disks is where you got this from?

As for user documentation, we only have this:

Note:

Nothing more available at the time of writing.

Try to install any package whatsoever first for testing purposes. Not zerofree. Another package. To confirm the system isn’t severely broken. As per: Package Installation from Debian Package Sources

sudo apt update
sudo apt install hello

Run systemcheck.

systemcheck