In general (the K3 is old, I don't recall the details), Duokan will not install on a device which has our jailbreak system installed.
What reason do you have for wanting to install Duokan?
If only for its handling of e-book displays - - -
Then I suggest that you try one of our e-book reader applications.
The forum members here have produced some very good e-book readers.
Try this one before installing Duokan:
https://www.mobileread.com/forums/sho...d.php?t=198742
(Note: read entire first post, including using the KUAL menu near the end){*}
Duokan proprietary?
The Duokan developers would like to think so.
Reading this forum you will find some very strong opinions expressed by the supporters of Open Source Software (myself included) on this subject.
{*} We have two "menu systems" here -
The KUAL (cool) application launcher is text-based and works on all Kindles except the K1;
The "Kindle Menu" system, which is image based, very easy to use, but only works on the K5-Touch and the K5-Paperwhite(gen 1) devices.
(Well, three, but KUAL has pretty much replaced the original launcher system.)