OpenSUSE MicroOS fails to start on OpenStack

I'm testing some operating systems cloud images to be used on OpenStack. I'm trying OpenSUSE MicroOS with the following butane configuration:

---
variant: fcos
version: 1.1.0
storage:
  filesystems:
    # Mount /home folder (required when creating non-root users)
    - device: /dev/disk/by-label/ROOT
      path: /home
      format: btrfs
      wipe_filesystem: false
      mount_options:
        - "subvol=/@/home"
  files:
    # give a name to the instance
    - path: /etc/hostname
      mode: 0644
      overwrite: true
      contents:
        inline: ${hostname}
passwd:
  users:
    # Define a password for root user
    - name: root
      password_hash: ${root_pass}
    # Create a new non-root user
    - name: ${username}
      ssh_authorized_keys:
      - ${ssh_pub_key}

I render this configuration to ignition and then I pass it to the instance user_data.. It works with Fedora CoreOS, Flatcar Linux and Ubuntu cloud-init, but MicroOS instance does not start..

I do not know what it could be wrong. I tried also with the following cloud-init configuration:

#cloud-config
mounts:
  - [/dev/disk/by-label/ROOT, /home, btrfs, "defaults,subvol=/@/home"]
users:
  - name: ${username}
    ssh-authorized-keys:
      - ${ssh_pub_key}

hostname: ${hostname}

I do not understand what prevents MicroOS instance to start...