As @emitorino hinted, we have discussed whether using classic for this would give a better signal that this can escape confinement. There’s been varying opinion (it is not an explicitly mentioned category in the classic process page, see also restic discussion) whether classic is appropriate for backup applications but in is generally true that during restore many such applications will need to be able to write to places that allow them to escape confinement. The main reason to pursue a confinement route would be for cases where Ubuntu Core is the desired installation target. Classic also needs vetting. It also true that for desktop a combination of read permission and in-progress prompting support on write might cover some backup cases, this approach is not immediately available though.