As I have said before, I think in-person voting fraud is, in most cases, a non factor. The ratio of effort/number of involved actors/risk of discovery/etc is not congenial.

However, its extremely well documented how vulnerable electronic voting machines and voting tabulation systems are. Go google up some state reports on it. Or google up some independent analysis from security experts.

When considering attacking the vote tabulation mechanisms themselves, the ratio risk/reward/number of actors involved/risk of discovery/etc looks much more favorable. As such, it seems wise to be actively aware of the possibility and question the role it might be playing. People should be suspicious, and should share and spread that suspicion - trust in the system should be undermined, because it is unworthy of trust. If people come to grips with this, either electronic voting will be eliminated or at least security will be taken more seriously.

Also, there was a mega fuckton of evidence of polling shenanigans during the GOP primary. There is also evidence of shenanigans for past Presidential elections.

Your assumption that the only shady stuff that makes an impact is gerrymandering is just that - an assumption, and not one that is well grounded. Just because there is no public incontrovertible proof that it has happened does not mean it hasn't happened, and it doesn't mean that powerful interests - including foreign govts - haven't been clued in and arent tempted to take action in the future.

For who could be free when every other man's humour might domineer over him? - John Locke (2nd Treatise, sect 57)