[drblah]

This, exactly. I work with similar modems daily. The first thing I do is to run the AT command for enabling adb. From there you can do whatever. The modems are quite beefy, 100s MB of RAM and multiple CPU cores. They even come pre-installed with a http server, ftp client, ALSA and much more.

Also, if you really want to get creative, I think you can just dump the firmware, which is just normal Linux. So just dump it, mount the filesystem and make whatever changes you want then re-flash.

The quality and security of the software in these things is absolutely bottom tier.

[solarkraft]

Do they need all that power? Sounds like it's more of an SoC with a modem than just a modem. Why then have another processor?

[electricant]

The market for cellular modules is very competitive. From a time to market point of view is cheaper and faster to reuse smartphone-grade socs instead of reinventing the wheel.

As far as I know, only u-blox is producing their own SoC (albeit for cat-m/nb-iot only) all the others are using existing solutions from Qualcomm and others.

This is only scratching the surface. I did not talk about certification which is another beast altogether.

[contingencies]

If you had to implement secure 4G/5G in an embedded environment, which hardware or approach would you reach for?