how do i set a static ip for my plex server htpc?
What is the Firmware? I am assuming you are on 3.x.
First figure out what your Plex server MAC address is( will probable be under clients in the GL.iNET admin panel) and just follow the document procedure. Lots of info in the documents section.
Static Ip setup document:
I do not work for and I am not directly associated with GL.iNet 
That didn’t help at all. I think I need upnp, I saw nothing about that in there
I now there is luci-app-upnp
You will need to install LuCi for that, I don’t now of GL.iNet Plugin. Ask @alzhoe for help with that if possible
Its under Services in LuCi
Please don’t create different post for the same problem
You are using openwrt build software: