NSA (not to mention foreign and organized crime actors) will have a field day rigging elections using back-doors on servers processing on-line voting, not to mention hardware and software rigging of various kinds at each step in the process.
I have _zero_ confidence in any tech solution.
Snowden explained how it works.
Why aren't the NSA and "crime actors" stealing my bank accounts and my crypto?
Because it would be noticed. We can't make anything tamper-proof (except possibly with quantum tech), but we can put in procedures and checks to make sure we would notice if our votes were discarded or flipped. Starting with the ability of each voter to audit how their votes were tabulated.