If you look up the 1876 presidential election, you will find that four states failed to either certify their elections or their certifications were disputed by Congress. Neither candidate got the majority of the electors because of the three disputed states. This led to a creation of a committee of five senators, five reps, and five Supreme Court justices to decide on how those states would pick their electors, and Hayes won. I think our best bet right now would be to either fail to certify at least Penn, Georgia, and one more state so that Biden doesn’t have the majority. Even if they do certify the states, they have to be accepted in January by Congress. So there is also a way in January to dispute a states certification when a complaint is filed by at least one senator and one Rep. I could see this happening if somehow there is certification and more damning evidence comes to light in late December which forces the dispute. In 1876, they only decided the president three days before inauguration and I think it will be similar for Trump.