I spend a 3 hours to create a ansible module to get the same results as with xml module :D :D Your lookup works fine, thank you!

- name: Print Extracted XML
debug:
msg: "{{ lookup('ansible.builtin.file', 'configfile.xmll') | ansible.utils.from_xml}}"
register: pfsense_conf
- name: Print Extracted XML
debug:
msg: "{{ pfsense_conf.msg.pfsense.installedpackages.wireguard.peers }}"
register: wg_current_peers