Notice that it's only mobile where that's a problem; x86 machines have apparently been doing the impossible for ~30 years now. And no, modems aren't an excuse; the modem itself can't be FOSS (probably) but it's just a self-contained device running its own firmware; there's nothing stopping you communicating with it via FOSS drivers.

Did you miss the first, say, 25 years of the 30? Because I have literally reset my video driver blindly from terminal once, because it just failed after an update, and similar stuff. Also, this is pretty much due to the oligopoly of a few entities in hardware space, making it easier to support said devices, and standards.

Phones aren’t built from a small selection of devices, and they often have patented firmware that the phone manufacturer couldn’t even publish even if they want to. As I shown, look at the best attempt at building an open-source phone. It sucks majorly.

Although I have thoughts on the matter, I'm not actually arguing about the quality of drivers, I'm arguing that x86 linux has had minimal problems with keeping all drivers in-tree, and if vendors want to support linux they've generally had no problem working with that. It is for some reason only mobile and embedded vendors that find it impossible to upstream drivers and that insist on shipping hacked-up vendor forks of ancient kernels.

And again, firmware is a separate matter; there's plenty of cases of linux shipping blobs for the device to run, so long as the driver to talk to that device is FOSS.