The state legislatures can give their Electoral College votes to Trump
Technically, with a very broad interpretation of the powers of the states according to the Constitution, they might be able to do so. It would come before the Supreme Court to decide if that interpretation is reasonable, should it ever happen in real life.
In reality, all of the States have election laws. None of them in *any* State currently allow for this scenario. If the law(s) were changed after the votes were cast, or someone managed to overturn them, then it would only apply to the next election, not this one. This did not happen; no laws were changed. No state governments decided to openly violate their own election laws, which could result in a real mess if they did. Yes, team Legalo Trumpo tried to challenge the laws in the states Biden narrowly won, *after* the vote was cast, but they failed utterly, so it won’t even affect the next election, let alone this one.
Trump lost on every conceivable level. The Electoral College vote is now finished, and Biden is now truly, officially, the president-elect. Trump’s only remaining hope is a coup, and the various branches of the military already said they aren’t going to support that. I’d say “good luck, buddy”, but only in the most sarcastic manner possible.