I'm on the verge of hard bricking my Fire tablet because the instructions on the [root][5.1.1] do not work. If someone could please retrieve the latest lk.bin from 5.1.1 stock (the latest Amazon made ROM), or from a custom rom that has been installed on top of FireOS 5.1.1 (by using FlashFire) and upload it, I would be greatful.
It's easy to do, and there isn't a risk of damage to your tablet. You do not need root, just adb shell access.
Run in adb shell:
dd if=/dev/block/platform/mtk-msdc.0/by-name/UBOOT of=/sdcard/lk.bin
and you should be able to find the lk.bin file on your internal storage (with a file manager or with Android File Transfer).
Thank you for doing this, as I will be able to use my tablet without fear of it running out of battery and never starting again!