My solution.
1) Cancel the league
2) Award the dippers the title. Annoying but fair, really.
3) Nobody relegated
4) Euro slots is the difficult bit, clubs will moan one way or the other, it might have to be based on what the positions are based on every team having played each other once
5) Next season, plan on two regional leagues to reduce games because there's a chance this virus could re-appear in winter if there's no vaccine in the mean time.
God knows what the championship and leagues below do.