[rendaw]

Kubernetes/k3s on a single node turns what could have been immutable 1-step upgrades into multi-step mutable upgrades, since kubernetes's software itself and all the management components you need are a mutable layer on top of the operating system.

[threeseed]

a) It doesn't have to be mutable. You can easily setup k3s on a single node, install the apps and bake an AMI or equivalent. And using something like ArgoCD or GitOps will ensure that your k8s stack is in sync with a tracked and managed Git repository.

b) In what world is upgrading your entire platform ever a single step. Even for a basic Python app you still have Python itself plus dependencies. And then of course whatever front end web server you're using.

[angio]

You can use Talos linux for an immutable (and tiny) OS.