This container can be pulled via:
  docker pull registry.opensuse.org/isv/rancher/elemental/maintenance/5.5/containers/rancher/seedimage-builder:1.4.4
  docker pull registry.opensuse.org/isv/rancher/elemental/maintenance/5.5/containers/rancher/seedimage-builder:1.4.4-3.18

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.