RT-Thread is an open source IoT Real-Time Operating System (RTOS).

The seL4 microkernel

A portable microkernel-based multiserver operating system written from scratch.

🏢 An operating system inspired by brutalist design that combines the ideals of UNIX from the 1970s with modern technology and engineering

MIT 6.828 Operating System Lab https://pdos.csail.mit.edu/6.828/2018/schedule.html

华为鸿蒙分布式操作系统（Huawei HarmonyOS，纯血鸿蒙Harmony Next ），开源鸿蒙分布式操作系统（ OpenHarmony）开发技术交流，最全鸿蒙技术资料库，手册，指南，共建国产操作系统万物互联新生态。

An efficient and secure microkernel built for ARM Cortex-M cores, inspired by L4

Ghost, a micro-kernel based hobby operating system.

A microkernel-based hackable operating system.

『自作OSで学ぶマイクロカーネルの設計と実装』サポートサイト

Tools and runtime for launching unmodified container images in Trusted Execution Environments

Portable asynchronous microkernel implementing multiprocessor priority scheduling and Unix-like abstractions

Phoenix-RTOS microkernel repository

Codezero Microkernel

MoonOS (just a kernel atm) is a micro kernel designed for the x86_64 and arm architecure.

POK kernel. Safe and secure for safety-critical systems.

An microkernel focusing on hyperadaptability, hyperreusability, and hyperdeployability.

MultiZone® Security TEE is the quick and safe way to add security and separation to any RISC-V processors. The RISC-V standard ISA doesn't define TrustZone-like primitives to provide hardware separation. To shield critical functionality from untrusted third-party components, MultiZone provides hardware-enforced, software-defined separation of multi

Simple GUI based Operating System - Based upon my own Microcokernel, heavily inspired by the original 1980s AmigaOS (though somewhat simpler).

Yet another cross-platform microkernel operating system, runs on x86/x86_64, arm64 and RISC-V