Comment by adrian_b
That would be desirable but it does not happen in practice.
All the USB network devices that I have ever used required specific drivers. Sometimes the drivers happened to be already bundled with the Linux kernel or with Windows, but frequently they were not.
Where do you buy such things? Every USB Ethernet card I've used in the last 10 years was either RNDIS or some version of USB-CDC. They've worked out of the box on both Linux, Windows and some even Android.