You need a system for point of use verification of system integrity by the voter as they are voting. It also doesn't need to be "simple enough" for anyone to d

You need a system for point of use verification of system integrity by the voter as they are voting. It also doesn't need to be "simple enough" for anyone to do it. You just need a system in place to enable voters to verify the authenticity of the machine (a relatively easy way is a public voting ledger where the voter can match the id the machine shows with what shows up in the ledger a minute later) and those with the know-how will do so.