There's plenty to audit. Does the number of votes match the number of voters? Are there chain of custody records. Are there envelopes for the mailed ballots? Are all the mailed ballots actually registered voters, and were they actually mailed? Furthermore, what mechanism was used to ensure that voters did not double vote by voting both in person and via absentee?

There's been reports of thousands of votes not being counted or added to the transmitted counts in various jurisdictions. That means at least part of the system broke down.

No, that means the people reporting these massive numbers of votes not counted are liars.

There is ample statutory and regulatory provision in every state for processes that confirm every aspect of what you are questioning. It’s as if you know nothing about elections or election systems.

It means that the processes failed, weren't enforced, either willfully or negligently.

If someone is able to report the wrong number of total votes, it means all the controls in the process weren't followed or simply doesn't work. The burden of proof is on the people holding the election to prove it's valid. So far, 'certifying' results is a rubber stamp, there's no actual certification being done.