The Eltanin is a project to develop an operating system, with focus on simplicity and coherence in mind, you can read better about its objectives at: https://eltaninos.org/

It already has a considerable amount of work done: the POSIX core utilities (ecore), a reproducible ports (arbor), a build system (redo), a POSIX translation layer for tertium (simia), an alternative library C (tertium), and a functional package manager (venus).

At the moment effort is being done to unite and put use of this userspace in a Linux distribution (Glacies)

If you have interest in this project or any of the tools produced in it, consider helping the project grow, become a sponsor and/or make part of the community: https://eltaninos.org/community