ereaders and syncing

The Xteink X4 I ordered a while back came in today, which sent me down a bit of a rabbithole on modern ereader tech. H/T of course to Laura for finding this weird little thing. The X4 is a nifty little device. It's cheap (comparatively, for other ereaders, at $70 USD), based on the extensible and well-documented ESP32 chip, and has a noteworthy tiny size. Famously, they market it primarily as a device that can be magsafe'd onto the back of a traditional phone. I think that's cute, for sure, but for my uses that's mostly a neat bonus instead of the main feature, which is that it is tiny and also light, two features that modern tech unfortunately lacks. It does have WiFi support, and a microSD reader, though beyond that it's a very simple device. It's not even a touchscreen, it has instead a modest complement of buttons on the front and sides. It does not have anything near the horsepower to act as a phone replacement, but I do agree with the Xteink (which I am, for the record,…