It's worth trying to understand what problem this executive order is purporting to solve. It's not clear; you have to squint.
Trump and many of the election deniers have created a widespread impression that mail-in ballots are unsecured, and that there are no (or only ineffective) safeguards against sending in counterfeit, fake, or duplicated ballots and having them counted.
But, despite being repeated frequently, this impression is completely false and baseless, as I'll discuss.