What was the last thing Schneier wrote on it? I thought it was this:

I don’t think it’s real. Yes, it’s plausible. But first of all, if someone actually surreptitiously put malicious chips onto motherboards en masse, we would have seen a photo of the alleged chip already. And second, there are easier, more effective, and less obvious ways of adding backdoors to networking equipment.

https://www.schneier.com/blog/archives/2018/11/that_bloomber...

I don't believe that there was ever extra chips being added to the boards, but what I could believe is that they shipped with firmware on specific chips that enabled data exfiltration for specific customers and due to a game of telephone with non technical people it turned into "they're adding chips inside the pcb layers!"

There also was a CEO of a hardware security company that came out and said that his firm had found an implanted chip during an audit. IIRC, he was convinced that it was very unlikely to be limited to Supermicro hardware.

Schneier was simply taking at face value the contents of the Bloomberg article, especially the statement by Mike Quinn who claimed he was told by the Air Force not to include any Supermicro gear in a bid.

No evidence was ever presented and nobody ever found anything, as far as I can tell?