Prerequisites

CentOS (7.0+), Debian (9/Stretch+) or Ubuntu (16.04+) server. This playbook can take over your whole server or co-exist with other services that you have there.
Python being installed on the server. Most distributions install Python by default, but some don't (e.g. Ubuntu 18.04) and require manual installation (something like apt-get install python).
the Ansible program being installed on your own computer. It's used to run this playbook and configures your server for you. Take a look at our guide about Ansible for version requirements or alternative ways to run Ansible.
either the dig tool or python-dns installed on your own computer. Used later on, by the playbook's services check feature.
an HTTPS-capable web server at the base domain name (<your-domain>) which is capable of serving static files (unless you decide to use DNS SRV records for Server Delegation)
properly configured DNS records for <your-domain> (details in Configuring DNS)
some TCP/UDP ports open. This playbook configures the server's internal firewall for you. In most cases, you don't need to do anything special. But if your server is running behind another firewall, you'd need to open these ports: 80/tcp (HTTP webserver), 443/tcp (HTTPS webserver), 3478/tcp (STUN over TCP), 3478/udp (STUN over UDP), 8448/tcp (Matrix Federation API HTTPS webserver), 49152-49172/udp (TURN over UDP).

When ready to proceed, continue with Configuring DNS.