It is an isolated peripheral in many smartphones. Whatever you do, there is of course a risk malicious code could break out of the isolation, true for your Ethernet proposal too.
Re:I want a computer that I own
by a1369209993 on Tuesday March 09, 2021 @02:57AM
(#26396453)
Having a malicious device on the other other end of a Ethernet connection is much less of a problem than having a malicious device that can DMA into main memory, which is something the baseband in Apple/Android phones at least allegedly can do.
This hasn't been true on iOS devices for a while, and I would expect that Android device manufactures have been making improvements here as well.
I could imagine a family of cellular and Wi-Fi devices that present as Ethernet bridges. They'd offer a configuration interface reminiscent of home routers (go to a magic IP either with a REST API or a browser-controllable menu). This eliminates a lot of the delicate, externally facing configuration options and has the side benefit of eliminating a lot of driver development hassle, especially on low-popularity OSs.