After reading the review of the Onyx BOOX Poke3 by @KelsonV I had a look at the BOOX range and ordered the BOOX Page. Here it is, on the right, next to my Kobo Clara HD.
So far, it has been good. I've installed the Android versions of Libby, Pocket and, yes, Firefox and they work fine. I've adjusted the E Ink refresh rates and button settings for the apps to work correctly.