How to install firmware on Kobo Libra 2 SD card ?

[SRu]

Hello,

I have a concern with a Kobo Libra 2, and I first mention that I'm a beginner regarding reader maitenance or upgrade operation...

The device is stuck, white screen, permament flashing led. The reader is not reachable when I connect it to a computer. I tried factory reset process, but the device doesn't respond at all. I kept the reader on the charger full night, no improvement. I opened it, checked the battery. It sounds OK. So I carefully removed the SD card. I can read it now on the computer with an adapter (Windows 11 computer).

Now I would like to totally reset the SD card with a new firmware as I'm suspecting a firmware corruption. Current SD card contains of version file:
N418267020350,4.1.15,4.38.21908,4.1.15,4.1.15,0000 0000-0000-0000-0000-000000000388

I downloaded kobo-update-4.31.19086.zip and kobopatch_4.31.19086.zip from the forum. Hopefully this version make sense with my device …

I would really appreciate if someone could :
- confirm if those files are ok for this device?
- provide a step-by-step procedure to "flash" the SD card (one more time, first time I try to maintain the reader)

Last point, hope this message will be clear, as I'm not a native English spoken guy … :-)

Thanks in advance for your help
SRu