F9 is an L4-inspired microkernel designed for ARM Cortex-M, targeting real-time embedded systems with hard determinism requirements. It implements the fundamental microkernel principles—address spaces, threads, and IPC, while adding advanced features from industrial RTOSes.
↫ F9 kernel GitHub page
For once, not written in Rust, and comes with both an L4-style native API and a userspace POSIX API, and there’s a ton of documentation to get you started.
I was going to ask why L4-inspired and not L4/seL4 compatible but reading the documentation they have extensions for embedded real-time. Even if that’s the case they should provide the compatibility to be able to use L4 or seL4 ecosystem. Otherwise more reinventing the wheel and duplicated/wasted effort.