Completely remove flatpak from moms computer, regaining ~10GB of space. Started getting low disk space (~500/mb) warnings. This was on a 30GB root partition. Using the terrific Filelight disk space utility, I identified flatpak as the culprit! I only had installed 4 flatpack programs and found a non-flatpack install for Signal, nothing else was important to me. Removing these only made a small dent in disk space usage. So I used Software Manager to remove flatpack itself, which still didn't help much. A lot of Flatpak related files, and hence space remained! So off to google where I found this solution How to completely remove flatpak . I decided on the following solution.
```
I would recommend reinstalling flatpak and running the following commands:
flatpak uninstall --unused
sudo apt-get remove --autoremove flatpak
sudo apt-get purge flatpak
```
The 1st step reclaimed a lot of space.
The 2nd step scared me because, at a glance, it looked like it was removing a lot of non-flatpak programs.
I was actually concerned that the computer would reboot...but it did!