Immutable operating systems in Linux refer to systems where the underlying file system is generally set to be read-only, preventing any modifications to the core system files once it’s booted. This design ensures that the system remains stable, bootable, and resistant to unauthorized changes.
Just like with many aspects of technology, there can be multiple expressions of the same idea. So when I asked Richard Brown a while back what were some misconceptions he wished were cleared up in regards to Aeon OS, here is what he said, along with some commentary from the author. Note -this was a while ago, so might have a follow up to this down the road.
#1 “I can’t use Aeon OS or immutable systems because they are too locked down.” - RB
While the core idea is to mount the root file system as read-only during normal operation, many projects have allowed SOME folders to be writable to provide some flexibility for the user. Those who think everything is “read only root” don’t comprehend that with btrfs subvolumes and overlayfs you can have a read only root filesystem and still have plenty parts of the filesystem to write to.
For the Aeon OS project, /etc is one of them. This file is a great candidate for this exception since it stores system configuration files, executables required to boot the system, and some log files.
#2 “I can use “transactional-update shell” without worrying about breaking the system because its imumutable.” - RB
While “transactional-update shell” can be helpful if you are a dev for the project debugging things - the command should never be used.
It can be dangerous and brick the system. This is why you have many helpful commands that range from “sudo transactional-update pkg install {package name}” to Distrobox if you want to bypass the need to reboot after using TU.
“That it’s some kind of resourced SUSE-driven effort - it’s not, and it wholly depends on voluntary effort”-RB
While Richard Brown has touched many projects in both SUSE and openSUSE in multiple capacities, Aeon OS is NOT a SUSE backed initative. This can be a shock to some given most blur the lines between the entities. The fact is, Aeon is a very opinionated desktop experience aimed for power users who want to get work done and not “fiddle” with their work machine. They want to create clean and isolated environments via distrobox and container based workflows.
It may seem counterintuitive, but this very nature makes it a GREAT candidate for those who want a “chromebook” like experience. You get automated updates, an always bootable environment (in case the update fails, it reverts back to the previous snapshot), and a fast Gnome Software with Flathub (and ONLY Flathub) baked in. Imagine that - Gnome software with fast results that actually make sense from what you typed…RIGHT OUT THE BOX! 
Even as a release candidate, many have used AEON OS (formerly known as MicroOS Desktop) for 2+ years as a daily driver. The inherit nature of being an immutable tumbleweed with tweaks that are baked in to make it “just work” is a testament to how solid this system is.
It only makes sense that Jorge Castro, a huge proponent of immutable base systems, recommends anyone who is “just walking into this space” give Aeon OS a go; and that is saying something because he LOVES his Silverblue based project (source: https://youtu.be/PHSizIq6ajw?si=efu2T3yfd3dUTub0&t=677).
We are living in fantastic times in Linux. For this reason, I think now is a good time to test the immutable waters if you haven’t, and see where this new era, or “aeon”, in personal computing takes you.
-Profetik JOE