Paper ballots that we almost never bother manually checking against the insecure digital tallies unless there’s a very close race or explicit challenge to the count.
Nearly every state routinely does statistical audits of voting machines compared with paper records.
People hate to hear this but: statistics work. You can randomly sample a portion (say, 2% to 5%) of ballots and have effective certainty about how much fraud or error there is in your voting system.