Epubor is merely plagiarism. They take open-source code and sell it without crediting the author. You can have all the functionality for free.
I'm sure you're right, but I'm not sure I care. I mean obviously I would prefer they give credit where it's due, but even writing those tools in the first place is a felony in some countries. It's not like they're robbing someone of their livelihood and the value they add by putting Kobo, Kindle, Nook, and Adobe all in one place with a built-in format convertor is really high.
I just paid for it, downloaded the kindle app, and dragged the .awz8 file and it says it doesn't support the format!
I think you might be doing something wrong then? Maybe you have the wrong file? The Kindle For PC app should always give you azw files, not azw8 (even if it does use the newer format they're all just named azw).
It should show up in the epubor app on the Kindle tab after you install the kindle app and used it to download your books. No need to drag and drop from the file system it's all right there in the app. It finds Kindle, Kobo, etc and lists them.
EDIT - Make sure you leave the Kindle app running. I think it needs to be able to read the keys from memory or something.
Feels jank to pay for the book AND pay to free it, but that's the world we live in.