---
- name: Check that nebula hosts are not empty
  hosts: localhost
  any_errors_fatal: true
  tasks:
    - name: Check for one host
      ansible.builtin.assert:
        that: (groups['nebula'] | default([])) | length > 0
        fail_msg: "No hosts configured. Ending test."
        success_msg: "There are hosts found in the group."

- name: Setup nebula
  hosts: nebula
  strategy: free
  become: true
  roles:
    - rockylinux.nebula

- name: Verify they can ping
  hosts: nebula
  strategy: free
  tasks:
    - name: Ping all nebula hosts
      ansible.builtin.command: "ping -W 1 -c 3 {{ hostvars[item]['nebula_ip'].split('/')[0] }}"
      changed_when: "1 != 1"
      register: ping_check
      until: ping_check is succeeded
      retries: 15
      delay: 10
      loop: "{{ ansible_play_hosts_all }}"
...