This seems fishy in a couple of different ways.
I looked at https://results.arizona.vote/#/federal/47/0 and compared with what this guy is saying, and:
- He says 123K would have switched the results to Harris, but Trump won AZ by 186K votes.
- He says there were 123K bullet ballots for Trump, but I see 3,367,122 votes for president, and 3,326,283 votes for US senator, a difference of only 41k, around 1%.
There are other sketchy things about it. He lists his qualifications as "I have worked as the CEO or CTO at seven high technology firms including two which specialized in hacking and counter-hacking operations." That, to me, is a suspiciously high number, and it's weird that he doesn't name them, and hasn't talked with his presumably extensive contacts from running those companies to get some other people on board to co-sign the letter. Usually that's how these things run if they are not BS. Not just listing the number of companies he's been CEO of.
His speculation about how the hack could have happened, and its connection with Elon Musk's lottery and the bomb threats, is wildly sketchy to me. Usually in my experience, serious security people are very cautious about laying out too many details when they talk about how it "could have been done" and they try to keep irrelevant speculation out of it, even if it's in their mind, until they have some reasonable confirmation for it. If anomalies in the numbers of votes were enough, he'd have stuck with the numbers and linked to his sources for them. Likewise his speculation about how law enforcement could nab the programmers involved and compel them to testify is totally wrong, I think.
I don't know for sure, since I'm just reading it and reacting to it, but it seems to raise multiple types of red flags to me.