[UBUNTU 20.04] Subiquity installer does not accept user-data generated after manual installation

I'm installing Ubuntu 20.04 with a nocloud-net installation source on a z/VM guest. I'm currently limited to seeing installation output only through webhook reporter, because I cannot access shell on the target system during installation.

After manual installation a user-data to repeat the process automatically is stored in /var/log/installer/autoinstall-user-data. However, it has two issues:

- there is no "version" entry, so Subiquity does not accept it at all:
curtin start subiquity/core_validation:
curtin finish subiquity/core_validation: 'version' is a required property

- when I add version: 1, I get the following error:
curtin start subiquity/Keyboard/load_autoinstall_data:
curtin finish subiquity/Keyboard/load_autoinstall_data: None is not of type 'string'

Failed validating 'type' in schema['properties']['toggle']:
    {'type': 'string'}

On instance['toggle']:
    None

And when I change this too I get the related issues with netplan and storage configuration.

Kernel command line:
cio_ignore=all,!condev,!0.0.3695,!0.0.bdf0-0.0.bdf2 url=http://bistro.lnxne.boe/ubuntu/UBUNTU20.04/ubuntu-20.04-live-server-s390x.iso ip=172.18.76.38::172.18.0.1:255.254.0.0:m8330038.lnxne.boe:encbdf0:none:172.18.0.1 autoinstall ds=nocloud-net;s=http://t35lp37.lnxne.boe:8080/cfg/

User-data:
#cloud-config
autoinstall:
  apt:
    geoip: true
    preserve_sources_list: false
    primary:
    - arches: [amd64, i386]
      uri: http://archive.ubuntu.com/ubuntu
    - arches: [default]
      uri: http://us.ports.ubuntu.com/ubuntu-ports
  identity: {hostname: m8330038, password: /wjUJRFEEW5PA.CormpX2CYCxwoEAqGpB4sdIi8GgdJLd21tzNGDcZMDi0,
    realname: user, username: user}
  keyboard: {layout: us, toggle: null, variant: ''}
  locale: en_US
  network:
    ethernets:
      encbdf0:
        addresses: [172.18.76.38/15]
        gateway4: 172.18.0.1
        nameservers:
          addresses: [172.18.0.1]
    version: 2
  proxy: http://lnxproxy.lnxne.boe:3128
  ssh:
    allow-pw: true
    authorized-keys: []
    install-server: true
  storage:
    config:
    - {device_id: 0.0.3695, blocksize: 4096, disk_layout: cdl, mode: quick, preserve: false,
      type: dasd, id: dasd-dasda}
    - {ptable: vtoc, serial: 0X3695, path: /dev/dasda, wipe: superblock-recursive,
      preserve: false, name: '', grub_device: false, device_id: 0.0.3695, type: disk,
      id: disk-dasda}
    - {device: disk-dasda, size: 22153265152, wipe: superblock, flag: '', number: 1,
      preserve: false, type: partition, id: partition-0}
    - {fstype: ext4, volume: partition-0, preserve: false, type: format, id: format-0}
    - {device: format-0, path: /, type: mount, id: mount-0}