If you allocate 30 GB for / that seems pretty low these days for a desktop system. If you don’t have much space, it’s always best to go with regular repository packages

Here someone had 163 flatpaks and it used 8,7GB in runtimes. So I’m guessing the 30GB number is for whole of /.

I just checked out mine, I have 34 apps and runtimes use 3,1GB

Runtimes are shared in theory but not in practice.

I think three runtimes (newest freedesktop, KDE and GNOME) cover 90% of my flatpaks. Then there’s programs that use some EOL’d runtime and never get updated, which sucks