“‘Even after certification state legislatures can seat whomever they want as electors.’
actually, no, they cannot...”
You might want to re-read Article 2 Section 1 Paragraph 2: “Each State shall appoint, in such Manner as the Legislature thereof may direct, a Number of Electors, equal to the whole Number of Senators and Representatives to which the State may be entitled in the Congress: but no Senator or Representative, or Person holding an Office of Trust or Profit under the United States, shall be appointed an Elector.”
That doesn’t seem to indicate they cannot.