In some sense, Kubernetes is just a portable platform for running Linux services, even on a single node using something like K3s. I almost see it as being an extension of the Linux OS layer.

This is what I do for small stuff, debian vm, k3s on it for a nicer http based deployment api.

Yep, this is the way. Linux is just a platform for running services on one or more computers without needing to know about those computers individually, and even if your scale is 1, it's often easier to install k3s and manage your services with it rather than memorizing a bunch of disparate tools with their own configuration languages, filepath conventions, etc. It's just a lot easier to use k3s than it is to cobble together stuff with traditional linux tools. It's a standard, scalable pane of glass and as much as I may dislike kubectl, it's worlds better than systemctl and journalctl and the like.

Then why can't we put a wrapper onto systemd and make that into a light weight k8s?