[stand-by] Image viewer cashes Wings3D on Linux

[dgud]

One idea of flatpak (and similiar systems) if security, so flatpak applications will not see
the rest of your hard-disk.
Thus it will not notice your povray installation.

That's a bummer but flatpak installation will not see any renderers

Now you are using xubuntu and the linux build on wings3d.com/download is built on ubuntu 18.04,
so that build should work for you.