Extract the last two elements from a list, no matter the length

I have a list of hosts in Ansible, which will always have minimum three elements:

[server]
apollo
boreas
cerus

Using a fact similar to:

- name: Set loadbalancer hosts fact
  ansible.builtin.set_fact:
    loadbalancer_hosts: "{{ groups['server'][1:3] }}"
  run_once: true

Will return the last 2 hosts. However, I want to be able to extract the last two hosts, even if I add additional hosts, later on. For example, if my list of hosts becomes:

[server]
apollo
boreas
cerus
chaos

loadbalancer_hosts should be

 - cerus
 - chaos

See Array slicing. In Ansible, use the Python syntax:

  loadbalancer_hosts: "{{ groups.server[-2:] }}"

Given the inventory

shell> cat hosts
[server]
apollo
boreas
cerus
chaos

gives what you want

  loadbalancer_hosts:
  - cerus
  - chaos

- hosts: all

  vars:

    loadbalancer_hosts: "{{ groups.server[-2:] }}"

  tasks:

    - debug:
        var: loadbalancer_hosts
      run_once: true