...by paper ballot with no computers involved in any of the processes.
A voter registration system that was not digital and paper based only would be hackable by anyone in the registrars office not to mention exceedingly labor intensive. Just ask ant librarian who was around before computers how hard it was to maintain a card catalogue and anybody who used it could hack it by pulling a card out and sticking it in his pocket. Computers and software are essential for a registration system. Paper ballots are a possibility, but again who does the counting and is anyone checking their numbers. I counted paper ballots back in the old days before I was old enough to vote. Nobody checked my tallies.
Seems like a database of registered voters that lets you print out lists of registered voters for polling places would be helpful.