You can do it without the security issues of online though.

For example every election in Washington ballots are mailed out to every address on file, it’s very easy to print a ballot online if you didn’t get it in the mail, and until recently there have been no supposed issues with mailing ballots (postage is prepaid), plus there are dedicated dropoff boxes as well. And even with all that convenience turnout was 65% in 2016, though it is expected to be higher this year.