Ethernet is ubiquitous, fast, and simple. You only need two diffpairs (four wires) to establish a 100Mbit link, the hardware is everywhere, you can do Ethernet over long distances easily, and tons of the microcontrollers and SoCs support it, too. Overall, it’s a technology you will be glad to know about, and there’s hundreds of scenarios where you could use it. If you need to establish a high-bandwidth connection between two Linux boards in your project, or maybe a Linux board and a powerful MCU...