If congress doesn't certify EVs?

[Sir Mohamed]

Pretty much a hotly discussed hypothetical about 2024 after January 6. What does actually happen if a GOP congress doesn't certify the victory of Biden or another Dem? I'm sure Dems would file a lawsuit, but even if SCOTUS agreed that there was no voter fraud to change the outcome, doesn't it still require congressional certification? Congress doesn't have an obligation to follow such a court ruling? Or would GOP state legislatures just appoint "alternate electors".

I guess SCOTUS could still rule these alternate electors are unlawful, but would get us back to congress being required to accept Dem electors? With such a stalemate likely unresolved until January 20, the speaker would become acting prez?