https://www.mobileread.com/forums/sho...d.php?t=216960
Is a port of the Koreader Project that has a File Manager, later posts include mods, hacks, and info on how to make your files idden from the kobo processing.
https://www.mobileread.com/forums/sho...d.php?t=201632
Provides a good way to launch the Koreader as well as other useful applications.
Luck;
Ken