Folks, this isn't even a close question. There isn't a "How to remove a President if he shouldn't have been seated in the first place" clause in the US Constitution.
Impeachment and only impeachment is the "removal tool" bestowed upon the Congress. SCOTUS has no power, either implicit or explicit, to remove a President once he's been sworn in. Any conjecture to the contrary is pure folly.
but what about all the election, swearing in, appointees, laws, being null and void if he is found not legit. Biden would not be president it would have to go to Peeelosi till another cannidate or decision on what to do could be decided.
But I am profoundly under the impression there will be NOTHING DONE so that a national riot is avoided.