Well, there are big issues…. That would take far longer to sort out in court than anyone has time for.
Legally, under the Constitution, the President is selected by the vote of the electoral college. There is no requirement in the U.S. Constitution for the EC to vote according to public elections. The state authorities may be guilty of fraud and violating their own constitutional process - but the U.S. Constitution does not specify how electors must vote other than the state is to select them.
The question of "… Now what…" Would be one for the SC in regard to whether or not fraud invalidates the federal process as well.
However, it does throw many other elections into question and brings to the surface the issue that our government may very well not be legitimate and many parts of it, even local, only use democracy as a cover/excuse for their coup throughout history.
That amid a hyperinflation of the currency is sure to make for some interesting times in DC.