And despite approximately 60 lawsuits failing and a number of recounts showing no significant changes, the election is still being contested.
The Electoral College votes within the next 24 hours and there is very little chance of any electoral votes being disqualified or flipped before then.
The next serious opportunity to try to derail things will be January 6th, when the votes of each state are presented to Congress. It is possible to contest these in a state by state fashion, and it looks like some people plan to contest 5 states. If this happens, debate on each is limited to 2 hours, followed by a vote.
Even of a couple of states are disqualified, it won't change the outcome.
The final options for the current US president are:
Just leave.
Leave while declaring himself the "true" president and set up a "government in exile."
Attempt to get the military to support him in overthrowing the US Constitution.