States can't change their rules for certification of electors without a governor's signature. If a state tried to pull some nonsense like changing the selection of electors away from the process as encoded in law before Nov. 3, that'd be new law and (a) would require a governor's signature or a veto-proof majority and (b) may actually be ex-post-facto if the current law is structured such that it declares how electors related to the votes cast on Nov. 3, so could be stopped by state courts.

The fantasy that Republican state legislatures could steal the ability of the people of their state to choose the President is just that: fantasy.