no spaces in path on my end, its an interesting bug, because it doesnt effect every system or os, so i decided to test other random app images as well, and some have the issue and some dont, i hope they fix the bugs with it as i think app images are great (not so much for security but for ease of use) thats where flatpak is good, provided that people set their permissions correctly (to be fair they usually dont so devs just leave it loose to ensure it runs. its a pretty common set of issues that really needs standardisation. it varies so greatly between systems even apparmor features varies between distro’s. i think their should be enforcement of feature set minimums but alas there is not.
im trying to find ways around these issues in my spare time as well, so if anything pops up that immediately fixes it ill be sure to share it.
i dont how ever, recommend people start adding the userns clone to 1. it will open a can of security worms that most people cannot fix or configure making them vulnerable.