I have a potential solution for listing snaps using /var/lib/snapd/hostfs/ - see https://github.com/CanonicalLtd/ubuntu-package-manifest/blob/main/snap/local/list-snaps.py
I have created a new topic @ Reading tracking information of host installed snaps from another snap to try figure out how to read all info for each snap.
Even if I proceed as-is, is it possible to request auto connect for the system-backup interface for the ubuntu-package-manifest strict snap?