Thanks for the guide, it helped me unbrick my Kobo Libra 2 N418
I'll leave some notes here for future googlers.
- My original issue was that when I connected to a new wifi network, it seems to have tried to download a new update and then bricked itself (I had sideloaded NickelMenu a year or so ago and forgotten all about it). The white light at the front would flash/blink and I'd get a white screen. If I tried to reset the Libra 2, maybe it would go to a white screen with three dots, but it would always revert to the blinking light and white screen.
- Opening the case was easy with a very thin tool. I attach photos of the markings on the main PCB of my unit, the markings on the battery, and the markings on the little power button break-out board.
- My MicroSD card was glued in with a very thin (and very clear!) coating. I got it out by grabbing the sides of the chip with tweezers and wiggling it out (photo attached).
- The MicroSD card from my unit was completely corrupted, it refused to delete partitions and format no matter what software I used. A full replacement was needed. I prepared the new MicroSD card by deleting all partitions from it and adding a new lettered partition (with MiniTool Partition Wizard), and then formatting that new lettered partition with the SD Association's SD Card Formatter tool. I used Balena Etcher Portable to flash the image onto the card.
- I flashed the first revision image, but this didn't work. After the unit booted up and got to the language selection screen, it immediately turned off with a screen telling me that it needed to be charged. Since DNSB's message said that one of the changes between revisions was to the battery management chip, I reflashed with the Revision E image and that works fine.
- The unit's serial number no longer matches mine in the 'About' section. I don't know where to change this; I tried changing it in the .kobo/version file, but the change doesn't stick.
- The firmware wrongly announced that it was up-to-date. I updated it manually by extracting
the latest firmware .zip to the .kobo folder and restarting the unit.