Based on linux is no guarantee for stable, secure or privacy respecting software. Android is based on Linux. :-) And so is Remarkable, and some of the e-book readers.
I really like both the idea behind e-book readers and Remarkable, but they are often a very closed environment, so forget about most FOSS, if any. They want to make money on you, and that stops, if you use other software than theirs.
It’s good your mom tried. It’s sad she gave up so soon. I’ve helped 4 people switch in the past months. I’ve gotten even more people curious and more open to switch. A success is not only the switch, but that people start to realize that they can. In my opinion. :-)