@LivingLegend:
So:
1) KUAL = Kindle Launcher = active content = special kind of "book" = goes into "documents" folder >> appears on Kindle's home screen / Cover View as a book with "active" flag on bottom of cover (if you don't see it after copying the azw2 file make sure that the filter is set to "All items" and not "Books")
2) KUAL uses extensions system, you add extensions (add extra buttons to KUAL GUI) by adding some folders with files to "extensions" folder (
which is NOT inside the "documents" folder but is in the same level [= both folders are in Kindle drive's root].
So, you unpack the "koreader" subfolder from "extensions" folder inside archive you downloaded form KOReader's Github page to "extensions" folder on Kindle drive.
3) The downlaoder archive contains "koreader" folder containing bunch of files (= that is the actual KOReader Linux app, the other "koreader" folder is just KUAL buttons definition). You unpack that to the same level (drive root) with "documents" and "extension" folders.
To read the PDF/epub/whatever book you've copied to your Kindle you open KUAL/Kindle Launcher "book", go to "Koreader" submenu/ press the button, and choose whichever option you want (open the last book you've read or open file manager and browse the file-system to find and open some new book). Hint: you don't have to copy books you plan to read with KOReader to "documents" folder of your Kindle, the files can be anywhere on Kindle drive. I personally prefer not to have my PDF visible in Cover view because I don't read them using Kindle's default PDF reader. Also I've never bothered with trying "KPV Booklet" instead of KUAL.