This is very cool! You're right that not exactly what I'm looking for, but great to see nonetheless. I did see on the product Q&A page[0] that one of the questions was about plugging in a keyboard. The answer was:
"You can connect a wired keyboard to the Palma via a USB-C to USB-A OTG Adapter. After that, you can type in the Notes app and third-party word processor apps. "
"You can connect a wired keyboard to the Palma via a USB-C to USB-A OTG Adapter. After that, you can type in the Notes app and third-party word processor apps. "
Which sounds promising!
[0] https://shop.boox.com/products/palma