Was mentioned several times on the TUHS and/or COFF mailing lists, I found
https://news.slashdot.org/story/23/07/29/192248/building-a-better-server-oxide-computer-ships-its-first-rack
https://blog.jessfraz.com/post/born-in-a-garage/
The book recommendations on https://blog.jessfraz.com/post/books/ look interesting

See also https://hubris.oxide.computer/ for Hubris, a small open-source operating system for deeply-embedded computer systems written in Rust.