You had your Plex open to the public with that setup. That’s not secure at all, unless you wanted anyone to access it.
If you can port forward from your own IP and it’s kind of stable, you can run a wire guard server to access your network and Plex.
If you can’t portforward you can try a mesh network like tailscale… there are other solutions as well. The fastest apparently is netwmaker, but you need to have a server with public IP. You can use a cheap VPS.