This is an Ansible role for managing some aspects of Alertmanager not covered by the official Alertmanager role from the Prometheus project. Currently this includes configuring firewalld.
Include the role puppeteers.prometheus.alertmanager_misc. If you wish it to actually manage firewalld you need to define a variable:
puppeteers_prometheus_alertmanager_misc_manage_firewalld: true
See defaults/main.yml for a full list of parameters.