I also ended up checking my mrinstaller.log file, and found out that I've had this Kindle jailbroken for more than 4 years now!
Code:
[2016-05-23 @ 00:12:51 +0530] - Beginning the processing of package 'Update_usbnet_0.21.N_install_pw2_kt2_kv_pw3.bin'
Wow.
Thanks, once again - I'd already started to look for sane eInk devices that supported EPUB+OPDS, and there was nothing in my country.