The evidence would be in the system logs and server logs that showed the timestamped activities for each of the voting machines, who was logged on, what network access transfers occurred, etc.
The fact that this is not required by law to be made public (with IP/MAC addresses redacted) is evidence that the electronic voting system used is not transparent and must be assumed to be suspect. Without having a lawsuit in court Sidney Powell can not enforce the discovery necessary to retrieve this information. Her argument is that the software has been designed to cheat, the pattern of vote tallies appears consistent with previous vote switching frauds in Venezuela, and statistical analysis shows impossible volumes of processing. This should trigger further discovery in a normal case.
A hand recount would find that easily. I've been told in other threads that Dominion machines in Georgia had the cheating feature turned off. Another explanation was that the hand recount numbers were ignored when they didn't match. Neither explanation is very satisfying.