The transfer media itself isn't as important as the anti-tamper mechanisms used. If Dominion used hardware-based key attestation to sign results files and the central system only accepted a single tabulation file with a valid signature from each known system with multi-party sign-offs on missing results, that's probably a security measure they'd be proud of and would advertise. It's not bulletproof alone by far, but would help raise the bar by a good measure.

Given they don't, it's probably a shitty .csv file that anybody with hands-on can edit. That's the kind of system the lowest bidder will build and can only be "disproven" with a full hand recount of paper ballots.

I say this as someone who spends way too much personal and professional time working with computers and finds them unendingly fascinating: electronic equipment more complicated than a printing calculator has no business in any election.