I'm searching for a legitimate operating system that truly utilizes a microkernel architecture instead of a monolithic kernel like Linux. The criteria I'm looking for include stability for production or development purposes, atomic updates to prevent partial system states, and an immutable core OS to keep it read-only and secure. Are there any distributions or projects that uniquely blend these modern deployment features with a genuine microkernel design?
4 Answers
You might want to check out MacOS. It's not strictly a microkernel, but it gets close to that design. However, it's not immutable or atomic, and it's pretty much the only user-friendly option available that attempts a microkernel-like approach. Just keep in mind that it isn't a true microkernel. Also, Linux is definitely not what you're looking for since it's a monolithic kernel, not a microkernel.
Have you considered GNU Guix with Hurd? It's built on a microkernel and aims for a more versatile operating system environment. Although Hurd can be quite unstable, it's one option that meets your criteria. Just keep your expectations in check!
There are several microkernel operating systems you might find interesting. For instance, AmigaOS, although not x86 compatible, had an update recently. There’s also QNX, Genode, and even HarmonyOS. Check out Mach or the L4 microkernel family. Some of these might seem obscure, but they’ve had updates relatively recently.
If you're really interested in something modern, seL4 is worth a look. It's designed for high assurance and security and follows microkernel principles. It might be low-level, but it's definitely a unique project in this space.

Related Questions
Can't Load PhpMyadmin On After Server Update
Redirect www to non-www in Apache Conf
How To Check If Your SSL Cert Is SHA 1
Windows TrackPad Gestures