"Scan this paper with the Foo app or enter your secret number on the website to reveal your voting receipt." its harder, but not that much harder.
> prohibitively expensive to attack at scale
Not sure about that. The existing system often gets voter turn out above 100%.
Vote buying is an issue without receipts. See tax cuts for the high income earners (right), welface increases (left), etc. If someone pays you $200 to vote for them, is that substantially different from a $200 tax cut or benefit increase?
[1] https://www.sacbee.com/news/politics-government/capitol-aler...
> In addition to the problem in Habersham County's Mud Creek precinct, where it appeared that 276 registered voters managed to cast 670 ballots,
That's a mix of paper of machines, as well as a host of other problems