I don’t know in which context this could be used, but I could imagine several contexts. The example I gave above was a context I imagined where someone knocks on the door and there are several people inside and one of them asks who should open the door and say vem öppnar?.
So is this semantically locked into an antipassive interpretation or might it also be understood as reflexive or passive in the right circumstances?
In other words, would the sentences "The door opens." or "The box opens (itself)." use the verb öppnar or would they use different verbs/verb forms? The same question applies for all intransitive clauses.