AMP has a feature that will generate startup scripts that allow you to start an application outside of AMP the exact same way that AMP itself starts it. See the “Diagnosing Startup Issues” segment of this guide.
By starting the application outside of AMP, you can see whether or not the application behaves the same way without AMP involved. If it behaves the same, you can therefore determine that AMP is not the issue.
Your UFW rules don’t show anything that would block any incoming traffic, and since you can connect on the local network then it’s nothing to do with that machine.
The only possible difference I could think of - is if the router you’re using is some cheap ISP provided router that will only properly port forward to machines that advertise over DNS. The way you’d normally know this is if the routers interface only lets you pick from a pre-filled list of systems to forward to rather than an internal IP.
Your router and/or port forwarding is undoubtedly, 100% the culprit here. So what I’d like to see next - is the output of the command ip addr on the system running AMP, as well as your port forwarding rules on your router showing that ports 14444/14445 UDP are forwarded to the internal IP that shows up there.