Promoting teams and not relegating any could be based on positive discrimination, or whatever the legal term might be. The idea being obviously not doing harm to anyone, and taking only the positives.
However, this does not take away the relative unfairness to those teams below promotion teams currently in the Championship and lower leagues, who are dreaming of promotion. But in reality there is no way that can happen now. The alternative would be to cancel the season, and in that scenario those teams would not be promoted anyway.
Taking all this into account I feel like promoting two teams to higher leagues from each league and not relegating any would be pretty close to a best possible solution for everyone.