With Kubernetes you can schedule workloads in a number of different ways. Let’s say you insisted on having a shell and package manager. Run your favorite distro’s container as a DaemonSet. With the proper mounts and permissions you can do a lot. In other words use Kubernetes to do the things need to do. Then what role does the OS really play? Well in the case of Talos it’s only there to run Kubernetes.
You literally do not need more than the most basic of host-OS facilities to run any Linux workload you want in a pod, the OS just needs to run containerd and have a kernel, talos adds the management plane to that mix to make it useable, but the userland provided by the oci image will not see any difference at all than if it were running on Ubuntu; it will see the kernel.