Mail-in ballots are very susceptible to fraud. Even Jimmy Carter thought as much. Eliminate them. Eliminate ballot harvesting. REQUIRE proof of citizenship to register to vote. Verify citizenship of every registered voter and purge any not verifiable.
Third party audit the computer code in tabulators.
Require ID when voting (who doesn’t have a government ID anymore?? Kids need a birth certificate to play Little league!) All polls nationwide must be closed before ANY state result is disclosed.