This container can be pulled via:
  docker pull registry.opensuse.org/isv/rancher/elemental/maintenance/6.0/containers/rancher/seedimage-builder:1.6.6
  docker pull registry.opensuse.org/isv/rancher/elemental/maintenance/6.0/containers/rancher/seedimage-builder:1.6.6-2.16
  docker pull registry.opensuse.org/isv/rancher/elemental/maintenance/6.0/containers/rancher/seedimage-builder:latest

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.