Kindles, Kobos, and KoReader

I jailbroke my old Kindle Oasis a while back, and while I mostly kept using my Kindle Paperwhite, the limitations of the Kindle interface started to chafe. I have pretty crappy eyesight, and at night, in the dark, if I look up a word in the dictionary, I can barely read the font. The stock option allows changing to a larger font, but that is EVERYWHERE, and causes the Wikipedia lookup to cut off very quickly. So, not great. Really quite irritating, in fact. Another annoyance is the dictionary situation. Over the years I've purchased a few different ones, but haven't managed to get them to work on my Kindles. Particularly my Shorter Oxford English has been resistant. Not so with KOReader. I can have my pick of dictionaries, including an assortment of French/Spanish/Italian/Latin/language to English ones, so I can actually understand parts of classic novels! All I have to do is either download them directly using KOReader's interface, or copy compatible dictionaries into…