https://github.com/snapcore/snapcraft/blob/master/docs/snapcraft-syntax.md says: “ confinement (string) The type of confinement supported by the snap. Can be either "devmode" (i.e. this snap doesn't support running under confinement) or "strict" (i.e. full confinement supported via interfaces). ” I see from canonical-tech@ and some other merge requests that there's at least one other confinement mode, “classic”. The docs should probably mention it :)