> Unless they generate a paper receipt as well that the voter has to confirm before the vote is counted.

Indeed! I've volunteered at polling places where this is done.

I think one reason polling places have gravitated towards the "use paper ballots for everything, which are then scanned" option is because you're likely going to have something like that anyway, for mail-in ballots. It does bring problems, but you still have the paper to fall back to.