After your very last sentence, I’m not even sure what your point is here. You just listed a bunch of reasons you don’t think mail in ballots are safe, and then ended with saying the alternative also isn’t safe from vote buying.
Vote buying also does not appear to be a problem in the US electoral system, as another commented pointed out: in order to make a difference in the election, you’d have to buy enough votes that someone would be bound to tell on you.
Yea no, I get that, it's just that voting was still secure up until smartphones were ubiquitous. Now it's not.
It's not just about vote stealing per se, it's about any third party infraction of individual voting rights. It may not matter on a large scale, but it matters to individuals.
Not only that, but it matters that bosses can't coerce workers into voting for someone, or an abusive spouse, or any third party who might have an interest in swaying an election. It often doesn't take much to sway an election.
It becomes very problematic when a victim is unable to vote for someone who would stop abuse. For example, Russia decriminalizing spousal physical abuse. That same thing could happen anywhere, and then you'd have every asshole abuser at home forcing their family to vote for their choice.
Not having secure voting is a real problem, and one that is now unsolved thanks to smartphones.
With my remote voting, I can generate as many ballots as I want. If I want to make a dummy ballot that says I voted for any given candidate in order to fool someone it is easier than ever. Now instead of 1 physical ballot, I can generate multiple ballots, and do as I please with them.
That's a different security issue, not related to voter coercion.
There are checks to ensure votes aren't fraudulent, that's actually very easy and already done. You can send as many ballots as you want, but they need to be legitimised against a person. That's not such an easy grift. I believe
Vote buying also does not appear to be a problem in the US electoral system, as another commented pointed out: in order to make a difference in the election, you’d have to buy enough votes that someone would be bound to tell on you.