To start the firewall after you stopped it:

sudo systemctl start firewalld

systemctl is part of systemd - it starts and stops various services, shows statuses, lists available services, etc.

There is documentation on opening ports here, plus more details on enabling & disabling the firewall: https://docs.fedoraproject.org/en-US/quick-docs/firewalld/#_controlling_ports_using_firewalld

Reenable the firewall with

systemctl start firewalld 

Then get the current networking zone with

firewall-cmd —get-active-zones 

It will likely be called FedoraWorkstation, if not just replace that name with whatever it is called in the following steps.

Next you should enable the ports for Moonlight, which from a quick ddg search I think this should do it:

firewall-cmd —zone=FedoraWorkstation —permanent —add-port=47998/udp

firewall-cmd —zone=FedoraWorkstation —permanent —add-port=47999/udp

firewall-cmd —zone=FedoraWorkstation —permanent —add-port=48000/udp

firewall-cmd —zone=FedoraWorkstation —permanent —add-port=47984/tcp

firewall-cmd —zone=FedoraWorkstation —permanent —add-port=47989/tcp

firewall-cmd —zone=FedoraWorkstation —permanent —add-port=48010/tcp

firewall-cmd —zone=FedoraWorkstation —permanent —add-port=47990/tcp

Then reload the firewall with:

firewall-cmd —reload

Lmk if that works

Edit: added more ports needed for the WebUI and controller support. Check the docs here if you wanna see what each port is used for