I think the Democratic Party should just print up paper ballots and get scanning machines if they need to. I live in a very small district because I'm in an enclave just outside a city limit, so we always have to vote by mail. Very easy to do, and never any waiting (so good for social distance). Primary results don't really need to come out quickly, so scanning a bunch of ballots should not be a problem. Besides, then they have all those paper ballots if they want to do a recount. It's certainly safer, and experts have been urging states to adopt it so they have paper trails that can't be hacked.