“Unsurprisingly, very few people have heard of it, and even their Googling skills don’t come in handy.”
Lanai started as a small RISC core inside Myricom network cards, documented in public. Google bought out the core engineers in 2013 and upstreamed a Lanai target into LLVM in 2016. What it runs on now, nobody outside Google will say. A secret CPU in a public compiler is a strange kind of open source.