"Failed to connect to bus: No such file or directory" when running systemctl --user

[coaxial]

Using this image in molecule, with the following molecule.yml file:

---
dependency:
  name: galaxy
  options:
    role-file: requirements.yml
driver:
  name: docker
platforms:
  # From https://github.com/geerlingguy/molecule-playbook-testing
  - name: ubuntu2004
    image: geerlingguy/docker-ubuntu2004-ansible:latest
    volumes:
      - /sys/fs/cgroup:/sys/fs/cgroup:ro
    # command: ${MOLECULE_DOCKER_COMMAND:-"/usr/sbin/init"}
    # command: ""
    command: "/usr/lib/systemd/systemd"
    # privileged is necessary for systemd tasks
    privileged: true
    pre_build_image: false
provisioner:
  name: ansible
  inventory:
    host_vars:
      ubuntu2004:
        ansible_user: ansible
        ansible_env:
          USER: ansible
verifier:
  name: testinfra
lint: |
  set -e
  yamllint .
  ansible-lint .

and this Dockerfile.j2 (to add the ansible user:

# Molecule managed

{% if item.registry is defined %}
FROM {{ item.registry.url }}/{{ item.image }}
{% else %}
FROM {{ item.image }}
{% endif %}

{% if item.env is defined %}
{% for var, value in item.env.items() %}
{% if value %}
ENV {{ var }} {{ value }}
{% endif %}
{% endfor %}
{% endif %}

RUN if [ $(command -v apt-get) ]; then export DEBIAN_FRONTEND=noninteractive && apt-get update && apt-get install -y python3 sudo bash ca-certificates iproute2 python3-apt aptitude && apt-get clean && rm -rf /var/lib/apt/lists/*; \
    elif [ $(command -v dnf) ]; then dnf makecache && dnf --assumeyes install /usr/bin/python3 /usr/bin/python3-config /usr/bin/dnf-3 sudo bash iproute && dnf clean all; \
    elif [ $(command -v yum) ]; then yum makecache fast && yum install -y /usr/bin/python /usr/bin/python2-config sudo yum-plugin-ovl bash iproute && sed -i 's/plugins=0/plugins=1/g' /etc/yum.conf && yum clean all; \
    elif [ $(command -v zypper) ]; then zypper refresh && zypper install -y python3 sudo bash iproute2 && zypper clean -a; \
    elif [ $(command -v apk) ]; then apk update && apk add --no-cache python3 sudo bash ca-certificates; \
    elif [ $(command -v xbps-install) ]; then xbps-install -Syu && xbps-install -y python3 sudo bash ca-certificates iproute2 && xbps-remove -O; fi

# Create `ansible` user with sudo permissions and membership in `DEPLOY_GROUP`
ENV ANSIBLE_USER=ansible SUDO_GROUP=sudo
RUN set -xe \
  && groupadd -r ${ANSIBLE_USER} \
  && useradd -m -g ${ANSIBLE_USER} ${ANSIBLE_USER} \
  && usermod -aG ${SUDO_GROUP} ${ANSIBLE_USER} \
  && sed -i "/^%${SUDO_GROUP}/s/ALL\$/NOPASSWD:ALL/g" /etc/sudoers

I then try to run this task:

- task:
  systemd:
    name: myunit.timer
    scope: user
    enabled: true
    state: started

Which fails:

    TASK [Enable and start automatic backups] **************************************
    task path: /home/coaxial/dotfiles/ansible-playbook/tasks/backups.yml:39
    redirecting (type: connection) ansible.builtin.docker to community.general.docker
    <ubuntu2004> ESTABLISH DOCKER CONNECTION FOR USER: ansible
    <ubuntu2004> EXEC ['/usr/bin/docker', b'exec', b'-u', 'ansible', b'-i', 'ubuntu2004', '/bin/sh', '-c', "/bin/sh -c 'echo ~ansible && sleep 0'"]
    <ubuntu2004> EXEC ['/usr/bin/docker', b'exec', b'-u', 'ansible', b'-i', 'ubuntu2004', '/bin/sh', '-c', '/bin/sh -c \'( umask 77 && mkdir -p "` echo /home/ansible/.ansible/tmp `"&& mkdir "` echo /home/ansible/.ansible/tmp/ansible-tmp-1607193789.149203-1414406-197663461612289 `" && echo ansible-tmp-1607193789.149203-1414406-197663461612289="` echo /home/ansible/.ansible/tmp/ansible-tmp-1607193789.149203-1414406-197663461612289 `" ) && sleep 0\'']
    Using module file /home/coaxial/.virtualenvs/ansible/lib/python3.8/site-packages/ansible/modules/systemd.py
    <ubuntu2004> PUT /home/coaxial/.ansible/tmp/ansible-local-1411952lk472l08/tmpfevv6a53 TO /home/ansible/.ansible/tmp/ansible-tmp-1607193789.149203-1414406-197663461612289/AnsiballZ_systemd.py
    <ubuntu2004> EXEC ['/usr/bin/docker', b'exec', b'-u', 'ansible', b'-i', 'ubuntu2004', '/bin/sh', '-c', "/bin/sh -c 'chmod u+x /home/ansible/.ansible/tmp/ansible-tmp-1607193789.149203-1414406-197663461612289/ /home/ansible/.ansible/tmp/ansible-tmp-1607193789.149203-1414406-197663461612289/AnsiballZ_systemd.py && sleep 0'"]
    <ubuntu2004> EXEC ['/usr/bin/docker', b'exec', b'-u', 'ansible', b'-i', 'ubuntu2004', '/bin/sh', '-c', "/bin/sh -c 'MAIL=/var/mail/ansible USER=ansible XDG_SESSION_TYPE=tty HOME=/home/ansible DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus NVM_DIR=/home/ansible/.nvm LOGNAME=ansible XDG_SESSION_CLASS=user TERM=xterm XDG_SESSION_ID=c3 PATH=:/home/ansible/.cargo/bin:/home/ansible/bin:/home/ansible/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/home/ansible/.rvm/bin:/usr/local/go/bin:/home/ansible/go/bin XDG_RUNTIME_DIR=/run/user/1000 LANG=en_US SHELL=/bin/sh PWD=/home/ansible LC_ALL=en_US.UTF-8 EDITOR=/usr/bin/nvim /usr/bin/python3 /home/ansible/.ansible/tmp/ansible-tmp-1607193789.149203-1414406-197663461612289/AnsiballZ_systemd.py && sleep 0'"]
    <ubuntu2004> EXEC ['/usr/bin/docker', b'exec', b'-u', 'ansible', b'-i', 'ubuntu2004', '/bin/sh', '-c', "/bin/sh -c 'rm -f -r /home/ansible/.ansible/tmp/ansible-tmp-1607193789.149203-1414406-197663461612289/ > /dev/null 2>&1 && sleep 0'"]
fatal: [ubuntu2004]: FAILED! => {
    "changed": false,
    "cmd": "/usr/bin/systemctl --user",
    "invocation": {
        "module_args": {
            "daemon_reexec": false,
            "daemon_reload": false,
            "enabled": true,
            "force": null,
            "masked": null,
            "name": "borgmatic.timer",
            "no_block": false,
            "scope": "user",
            "state": "started",
            "user": null
        }
    },
    "msg": "Failed to connect to bus: No such file or directory",
    "rc": 1,
    "stderr": "Failed to connect to bus: No such file or directory\n",
    "stderr_lines": [
        "Failed to connect to bus: No such file or directory"
    ],
    "stdout": "",
    "stdout_lines": []
}

Furthermore:

coaxial@x230 $ molecule login
root@ubuntu2004:/# sudo -u ansible systemctl --user
Failed to connect to bus: No such file or directory
root@ubuntu2004:/# su - ansible
$ systemctl --user
  UNIT                                       LOAD   ACTIVE     SUB       DESCRIP>
  dev-mapper-ubuntu\x2d\x2dvg\x2droot.device loaded activating tentative /dev/ma>
  -.mount                                    loaded active     mounted   Root Mo>
  dev-hugepages.mount                        loaded active     mounted   /dev/hu>
  dev-mqueue.mount                           loaded active     mounted   /dev/mq>
  etc-hostname.mount                         loaded active     mounted   /etc/ho>
  etc-hosts.mount                            loaded active     mounted   /etc/ho>
  etc-resolv.conf.mount                      loaded active     mounted   /etc/re>
  run-user-1000.mount                        loaded active     mounted   /run/us>
  sys-fs-fuse-connections.mount              loaded active     mounted   /sys/fs>
  sys-kernel-config.mount                    loaded active     mounted   /sys/ke>
  sys-kernel-debug.mount                     loaded active     mounted   /sys/ke>
  sys-kernel-tracing.mount                   loaded active     mounted   /sys/ke>
  tmp.mount                                  loaded active     mounted   /tmp   >
  init.scope                                 loaded active     running   System >
  -.slice                                    loaded active     active    Root Sl>
  dbus.socket                                loaded active     listening D-Bus U>
  pk-debconf-helper.socket                   loaded active     listening debconf>
  basic.target                               loaded active     active    Basic S>
  default.target                             loaded active     active    Main Us>
  paths.target                               loaded active     active    Paths  >
  sockets.target                             loaded active     active    Sockets>
  timers.target                              loaded active     active    Timers >

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.

22 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.
$ env
MAIL=/var/mail/ansible
USER=ansible
XDG_SESSION_TYPE=tty
HOME=/home/ansible
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus
LOGNAME=ansible
XDG_SESSION_CLASS=user
TERM=xterm
XDG_SESSION_ID=c2
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
XDG_RUNTIME_DIR=/run/user/1000
SHELL=/bin/sh
PWD=/home/ansible
$
root@ubuntu2004:/# sudo -u ansible env
HOSTNAME=ubuntu2004
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=00:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.zst=01;31:*.tzst=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.wim=01;31:*.swm=01;31:*.dwm=01;31:*.esd=01;31:*.jpg=01;35:*.jpeg=01;35:*.mjpg=01;35:*.mjpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.m4a=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.oga=00;36:*.opus=00;36:*.spx=00;36:*.xspf=00;36:
TERM=xterm
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin
MAIL=/var/mail/ansible
LOGNAME=ansible
USER=ansible
HOME=/home/ansible
SHELL=/bin/sh
SUDO_COMMAND=/usr/bin/env
SUDO_USER=root
SUDO_UID=0
SUDO_GID=0

I have also tried setting DBUS_SESSION_BUS_ADDRESS: unix:path=/run/user/1000/bus for that task with environment, but it fails the same way. I then tried it again but with the whole environment as per the env command after su - ansible, and same error.

What I don't get is why is that command running directly in the container with su - ansible, but not in the task or with sudo -u ansible.