> "Docker images (even slimmed down) have an OS (most likely a Linux distribution)"

Not necessarily. Docker images can be based from the "scratch" container, and may contain only a single binary. With static compilation, the libraries can be included in the binary.

The O/S is provided by the container-host (which is usually a linux VM).

This doc describes building an image from "scratch": https://docs.docker.com/build/building/base-images/#create-a...