Cool, but any SBC that runs Linux and has a USB port that supports gadget mode can do this. Either way, what does this have to do with the article?

Most SBCs are larger. I was looking for the smallest iPad Linux sidecar, when I submitted this article. Here is one with RP2350, 1.5" display, USB-c and microSD, https://www.waveshare.com/rp2350-lcd-1.47-a.htm. Apple sold over 600 million iPads. Some of those could benefit from Linux sidecars to add functionality not available on iPadOS, increasing demand for small RP2350 boards.