Paper-ballot-backed elections are the solution.
Election cybersecurity will remain a hot topic going forward — even beyond 2020. See this Washington Post story, Trump’s embrace of conspiracy theories could endanger 2020.
I see the real answer is disconnecting the election tabulation and voter rolls from the larger cybergrid. And, having a back-up paper ballot is key. Even with paper ballots, there is so much citizen mistrust of government, many think "dead people are voting," etc.