> It would be nice if someone were to start working on an aftermarket linux distribution/ecossytem that targets eink devices. It's a lot of work to do, though, so I'm not surprised that nobody has picked up that torch yet.

That is what I'm trying to do with https://github.com/bjesus/air . Kobo runs mainline Linux quite fine, and specifically PostmarketOS works great. Assembling an interface that plays nicely with the device hasn't actually been that difficult!