Hey there,
I'm attempting to communicate with my GS810EMX via serial.
I have found a couple of connections that could be it, not knowing what the layout is.
The first connector has 10 pins, which I have not tested. https://imgur.com/a/jBW3NLr
Based on the available GPL download from Netgear this appears to be based on a single core Marvell Armada chip with Marvell switch so a likely candidate for an OpenWrt port!
OpenWrt is not currently available for this device. I am looking to acquire either the GS810EMX or GS110EMX to determine the feasibility of adding support.