Linux

But have been wondering why I haven’t heard of any immutable distros from arch based distros yet.

If your question is "Why doesn't Arch have its own atomic/immutable spin/flavor like Fedora and openSUSE have in their Silverblue/Kinoite and Aeon/Kalpa respectively?", then the answer simply lies in the fact that Fedora and openSUSE have a lot more incentive for venturing the unexplored waters of atomicity/immutability as their enterprise counterparts exist and will benefit majorly from it. And I haven't even mentioned how most of the new stuff first appear on Fedora (systemd, PipeWire, Wayland etc) before they're adopted on other distros.

The enterprise counterparts also allow funding that is essential for erecting this from the ground. But, even then, the shift towards atomic/immutable is a difficult one with a lot of hardships and complexity. From the ones that have developed their atomic/immutable projects retroactively (so GuixSD and NixOS don't count as they've been atomic/immutable (and declarative) from inception), only Fedora's (I'd argue) have matured sufficiently. But Fedora has been at it since at least 2017, so they've had a head start compared to the others.

In contrast to Debian (through Canonical), Fedora (through Red Hat) and openSUSE (through SuSE), Arch has literally no (in)direct ties to enterprise. Hence, it will only adopt an atomic/immutable variant if the incentive is high from the community or if it's very easy and only comes with major benefits. But, as even openSUSE is currently struggling with their atomic/immutable variants, it has a long road ahead before it becomes something that can be easily adopted by Arch. Hence, don't expect Arch's atomic/immutable variant any time soon.

However, if any derivative suffices, then at least the likes of blendOS, ChimeraOS and even SteamOS are worth mentioning here.