I think you actually want that to say global (under REGION). Due to…
Also, I’d release the IPv6 address, since UDP won’t be available over that. (Unless Minecraft can make do with TCP-only.)
If it’s a Debian-based image then you can apt-get update followed by apt-get install --no-install-recommends iproute2, which is a package of general IP networking goodies.
ss -unap will show all process that are listening on UDP at the moment. You need Local Address to match the entry for fly-global-services in /etc/hosts.
Hope this helps a little!