I have successfully jailbroken a new (refurbished) KV shipped with fw 5.10.2.
Some particular notes:
- I've used this adapter, with jumper placed at 1.8V. I've only needed 3 cables: TX, RX and GND.
- I've managed to use the no-solder-but-pins solution:
I've used a rigid rubber earphones case to hold pins in place.
- I've found special difficulty in closing the KV. This noismaster post has the key points to properly achieve KV closing.
Thanks to every poster in this thread, and in the
KV serial jb thread.