I was having difficulty getting my microphone to work in the OBS-Studio .pet from the quickpet in FossaPup64_9.5. I decided to give the flatpak a try and see if it would work.
Most of this 7.1G is /var/lib/flatpak/repo/objects 2.8G and /var/lib/flatpak/runtime 3.7G. I knew flatpak needed some storage, but didn't know that much!!
If you decide to do it, adding more flatpak apps isn't as painful. The OBS flatpak seems to be about 600mb. Personally I can't uninstall flatpak fast enough and avoid it like the plague in my Puppy OS's.