As an observation, there’s more going on with that OLD version of OpenWRT than just an old kernel. There’s things like it not working with modern USB 4G and soon to be out 5G modems, because they don’t function as a classic 3G, they’re a USB CDC-ECM device, which for the source branch you’re building out of , it just simply doesn’t work (The Black micro-bricks work just fine…but they’re using the latest LEDE derived OpenWRT…),
There’s more. It’s enough to be infuriated and deeply disappointed with GL-Inet, to be honest with you. It’s something you should’ve contemplated DEEPLY before designing the device in the FIRST place.
Someone needs to resolve this situation or offer an option for a build using the same, knowing peak performance may not be obtained. What is the performance degradation between the two classes of drivers and has anyone even looked to see if it’s an “old” issue and they’ve fixed it?