It's worth mentioning Microsoft's Midori, a follow-on to Singularity: https://en.wikipedia.org/wiki/Midori_(operating_system)

Joe Duffy, who worked on Midori, wrote some on his blog about it: https://joeduffyblog.com/2015/11/03/blogging-about-midori/

I wonder whether Midori could have been a contender for some of the WASI/WASM isolation packing lots of functions into one system, like Cloudflare Workers or Vercel Edge. Maybe Midori was ahead of its time.