The average person can't provide you proof. But we can point to mathematical incongruencies.
Prior to 2020, we had xxx number of ballots absentee or mail in etc. In each of those elections a % of those ballots were rejected due to signature issues or incorrectly being filled out etc. And those figures have remained fairly consistent.
Then 2020 hits, and the number of mail-in, absentee, drop box ballots EXPLODES. And the number of ballot rejections actually went DOWN?
So in elections prior to 2020... let's say 1 million people voted absentee/mail in per election. Roughly 3% of ballots would be rejected for various reasons. 2020 hits, and now we have 30 million mail-in/absentee ballots, with less than 1% rejection rate. That is a mathematical impossibility.