Do not flush the fw rules when docker is present.

tasks/disable-plain-iptables.yml

@@ -1,11 +1,21 @@
 ---
+- name: disable-plain-iptables | Stop the iptables firewall
+  when: docker_install is not defined
+  tags: ['iptables', 'iptables_rules']
+  block:
+    - name: disable-plain-iptables | Check if /usr/sbin/netfilter-persistent exists
+      ansible.builtin.stat:
+        path: /usr/sbin/netfilter-persistent
+      register: netfilter_persistent_executable
+    - name: disable-plain-iptables | Flush the iptables rules
+      ansible.builtin.command: /usr/sbin/netfilter-persistent flush && touch /root/.netfilter_disabled
+      args:
+        creates: /root/.netfilter_disabled
+      when: netfilter_persistent_executable.stat.exists is defined and netfilter_persistent_executable.stat.exists
+
 - name: disable-plain-iptables | Stop the iptables firewall
   tags: ['iptables', 'iptables_rules']
   block:
-    - name: disable-plain-iptables | Flush the iptables rules
-      ansible.builtin.command: /usr/sbin/netfilter-persistent flush
-      ignore_errors: true
-
     - name: disable-plain-iptables | Stop and disable the netfilter service
       ansible.builtin.service:
         name: netfilter-persistent