Mechanical voting machines, perhaps. Electronic machines aare easy enough to manipulate that one would wonder why any are not manipulated. The Dominion machines have an inserted at the factory algorithm that switches a set percentage of votes. It turns out also that virtually all of them in 2020 were attached to the internet though we were all assured that they were not.
Texas is switching to a system where each ballot will be recorded on paper too. In the mean time, every ballot is now recorded as a PDF, so it is possible to account for each ballot. The votes are not just recorded as totals for each race. No voting machines in Texas are connected to the internet or to a WiFi router. There are numerical sealed tags on the doors that close off the ports on the voting server/controller machines. The tags have to match up with what was recorded by the county clerk's office and by the election judge at poll opening and poll closing. You can't just plug in a USB device on the voting machines or the servers. Also the machines are not left unattended while precincts are open. Furthermore in Texas both parties are allowed to have a judge at each precinct. Also each party and each entity on the ballot is allowed to have poll watchers. I have worked every job on election day. I have been an election clerk, poll watcher, election judge, alternate judge, and recall worker. I know what I'm talking about.