Firmware for H850 Cellular Router

Hi, I have a H850 With Cellular Modem MU 736.
It's currently running a closed version of OpenWRT and I would like to update it to the current version of OpenWRT Firmware..
Problem is I cant access the Sim/APN settings on the closed version.

I don't see my model in the list....
Is there a version someone could recommend to try on this one.
This router has Lan/Wan/WiFi/3g/4g/GPS/WiFi Aux.
Their are GPIO pins on the back as follows;
DC-IN, GND, GPIO10, GPIO9, GPIO8, GND, GPIO7, GPIO6
Standard grey Chinese version of a 3/4g router
Thanks in advance! I used to be big on Tomato and OPENWRT back in the day and look forward to getting back in to it!!
Have a great day all!!

Unfortunately if it's not on the wiki or downloads then is unsupported.
But you can add support

So what's the process of adding support?

wiki?