Weird proprietary device (jiofi)

Hello there, I have a low-cost, small, closed source proprietary device, popularly known as JioFi in India. I'd like to flash openwrt or some other good unix-like firmware for it that gives some good control.

It seems very hard to figure out internals of it. On technical specs they have given 2GB RAM and 2GiB ROM.

It has a USB slot for USB tether / charging & can connect to a few devices. Basically it is a device to which I insert a 4G VOLTE sim (jio, of same provider) and get wlan hotspot for devices without LTE.

Given these things, How can I figure out about firmware and underlying OS? 2GiB of RAM is too redundant for such a device. I have heard they lowered it to 128 / 256 MiB in recent versions. CPU usage is around ~17% when single device is connected & 110-115 MiB RAM is used.

I couldn't find any internals documentation about this. How can I reverse engineer this black box? I don't want to waste that much CPU & RAM.

It is likely made by ZTE. They have a whole bunch of different models that get re-branded.

I think these are unsupportable because they run everything on one CPU chip, and the LTE stuff is closed source.

It should tether as a USB RNDIS device, which lets you use it as an LTE modem and have your own router.

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It is a vietnamese company, not ZTE.

By the way, I think it runs some heavily modified Linux or Android etc.. because of high amounts of RAM and ROM. I have heard that the recent version is equipped with ALT3800 or something like that name which gives altair-semi in google search.

Is it possible to get a shell account on it using some known exploit or something?