年末にAnsible勉強中です。
AnsibleでDockerをインストールするときにターゲットバージョンより、新しいバージョンがインストールされていた時の対処方法を備忘録として残します。
aptモジュールを使った他のパッケージのインストール時も同様の対処でいけるはず。

結論

forceにtrueを設定
dpkg_optionsにforce-downgradeを設定

main.yml

- name: Docker | Install Docker | apt
  apt:
    name:
     - "docker-ce={{docker_ce_version}}"
     - "docker-ce-cli={{docker_ce_cli_version}}"
     - "containerd.io={{containerd_io_version}}"
    state: present
    update_cache: yes
    force: yes
    dpkg_options: force-downgrade

実行環境

vagrant
- ubntu18.04
  - box-image:ubuntu/bionic64
  - 20201125.0.0
ansible:2.9.16

実行結果（失敗）

最初にオプションが不足したまま、実行して、以下のようなエラーが出力され、調査しました。

ansible実行結果

fatal: [192.168.xx.xx]: FAILED! => {"cache_update_time": 1609061762, "cache_updated": true, "changed": false, 
"msg": "'/usr/bin/apt-get -y -o \"Dpkg::Options::=--force-confdef\" -o \"Dpkg::Options::=--force-confold\"
install 'docker-ce=5:18.09.2~3-0~ubuntu-bionic' 'docker-ce-cli=5:18.09.2~3-0~ubuntu-bionic' 'containerd.io=1.3.7-1'
' failed: E: Packages were downgraded and -y was used without --allow-downgrades.",
 "rc": 100, "stderr": "E: Packages were downgraded and -y was used without --allow-downgrades.",
 "stderr_lines": ["E: Packages were downgraded and -y was used without --allow-downgrades."],
 "stdout": "Reading package lists...
Building dependency tree...
Reading state information...
The following package was automatically installed and is no longer required:\n
docker-ce-rootless-extras
Use 'sudo apt autoremove' to remove it.
The following packages will be DOWNGRADED:
  containerd.io docker-ce docker-ce-cli
0 upgraded, 0 newly installed, 3 downgraded, 0 to remove and 10 not upgraded.",
 "stdout_lines": ["Reading package lists...", "Building dependency tree...", "Reading state information...",
 "The following package was automatically installed and is no longer required:",
 "  docker-ce-rootless-extras", "Use 'sudo apt autoremove' to remove it.",
 "The following packages will be DOWNGRADED:",
 "  containerd.io docker-ce docker-ce-cli", "0 upgraded, 0 newly installed, 3 downgraded, 0 to remove and 10 not upgraded."]}

調査不足

ダウングレードするより、ターゲットバージョンと一致しない場合はアンインストールすべき？

参考

https://docs.ansible.com/ansible/latest/collections/ansible/builtin/apt_module.html
https://stackoverflow.com/questions/56332649/is-there-a-way-to-allow-downgrades-with-apt-ansible-module