SCOTUS could choose to:

-- Award electors to Trump in states like NV which have names and address of enough votes to change the outcome but which refuse to act

-- Decertify and allow the state legislatures to select a new slate of electors

-- Decertify all four states without providing the opportunity for new electors. This would leave neither candidate with a majority and send the matter to the state delegations in the House.

Bush v Gore threw it back to the state level but said that time had run out so the point was moot. That is not really the optimal way to decide the case.