Thank you for the explanation, Sohaib.
I reproduced your KUAL issue (I was actually using the Booklet version from the get-go -- hence didn't encountered this problem). After some digging, looks like method that MKK Kindlet JailBreak uses to skip Java security policy for Dev kindlets just doesn't work on 5.3.3, the patch -- in json_simple-1.1.jar -- doesn't have JailbreakerPolicy class ever activated. I ended up patching /opt/amazon/ebook/lib/KindletImplementation-2.2.jar to:
- Disable certificate verification
- Skip Application-Id manifest requirement
- Accept null applicationId
I used Claude to assist me with patching. I attach the patched jar and a python script that does the patching: the latter both for the paranoid, and to be able to double-check the changes.
The patched jar has to replace the FW /opt/amazon/ebook/lib/KindletImplementation-2.2.jar -- you should backup the existing one first.
The easiest way to do so is using KOReader's SSH server (dropbear), since you're already using KOReader.