When I began Ursula Le Guin's Worlds of Exile and Illusion I was using Kobo's Android app. But three chapters before the end they started feeding me ads to buy more Le Guin books, so I switched to Cool Reader, which is in F-Droid. It's a much more satisfying application, which gives total control over how the book looks, and is easier and friendlier, after you get used to it, than commercial e-reader apps. The Le Guin book (actually three books) was, I think released without DRM. But in Calibre I can easily remove Kobo's DRM. So far I've done this only with Kobo books, because in Linux it's harder with Kindle books. It seems you need to set up Amazon's Windows version under Wine in order to get the key that can be used to decode the book. I've just read that some Kobo books are sold more cheaply in the US than other places, so to get those cheaper prices, one has to appear to be in the US. Didn't know about that.

I have a Kobo e-reader, but it's software is a bit buggy. I have an NVidea tablet which a couple of weeks ago blank screened when I was in the middle of reading something and I haven't been able to wake it since, though it's a software, not a hardware issue. So I've taken to reading on my phone. It's a 3 year old cheap Micromax model, but it suits me well enough, except that I daren't try Lineage on it.