“a slate certified and appointed by the legislature will trump one certified by governor per the Twelfth Amendment,”
Only if the pertinent Congressional House decide so.
It is totally their decision.
So what is your understanding of what will happen should at least one state send a competing slate of Electors?
It sounds like you believe this goes nowhere because Congress will end up agreeing to boot Trump.
If so, does your opinion change if more than one State Legislature decides to send a competing slate of electors?