The default Z2JH cmd vs the container’s default cmd is a known point of confusion. In the forthcoming Z2JH 2.0 it’ll default to the container’s cmd which should be more intuitive! https://github.com/jupyterhub/zero-to-jupyterhub-k8s/pull/2449
Also see https://github.com/jupyter/docker-stacks/issues/1528 for more background
Note you shouldn’t need --allow-root since you’re not running the notebook as root, only the container which should drop to the unprivileged user after enabling sudo.