Operating systems written in Haskell

Greetings. I have found many sites discussing various projects to build a full operating system in haskell. All of them seem to be a good decade old. This indicates that there was definite interest in this at one time, but that it either didn’t catch on, or the projects went either classified, or people just stopped sharing them. I am currently trying to figure out what “the best” operating system would be, how it would be built. I am currently learning plan9, and oberon is interesting for ...