By default, the firewall will prevent connection to your 0ad server. To adjust that, you need to open up the port 20595 (UDP). This three lines create a Firewalld service called 0ad, attach it to the default zone and reload the firewall:
$ sudo firewall-cmd --permanent --new-service=0ad --set-description="0ad, A free, open-source game of ancient warfare" --add-port=20595/udp $ sudo firewall-cmd --zone=FedoraWorkstation --add-service=0ad --permanent $ sudo firewall-cmd --reload