Thanks a lot for all your help, David! Very kind of you.
In case it helps someone, my Kobo Touch N905C is now fixed.
It had a "restarting" boot loop after accidentally flashing the wrong firmware version for this model (mark 3 firmware on a mark 4 device, oops!
Read the wiki carefully.).
This is a helpful youtube video (titled "Upgrade your Kobo Mini ereader")
https://www.youtube.com/watch?v=73QGYk2q80M
How to fix the Kobo Touch N905C: (this process may be similar for other models but you must ensure you have the right microSD card backup image. I believe some models do not come with an internal microSD card though.)
You can use the free Windows software called "USB Image Tool" for flashing the backup image onto the Kobo's internal microSD card.
Download taken from the above youtube video description:
http://www.alexpage.de/usb-image-tool/download/
Hesitant to use Linux and the Windows software Balena Etcher did not work for me but USB Image Tool did.
You also need to obtain a backup microSD card image (.img file) for your model (N905C in my case), you can ask in this thread or alternatively you can borrow an exact same model Kobo from a friend and make a backup image of their microSD card using the same software.
Step 1: First check the Kobo has been charged for at least an hour and is actually the correct model (it's written on the bottom of the device itself, i.e. N905C is written on mine, not N905B or N905).
Turn it off by sliding the button thing for at least 15 seconds (so we know it's off and not just in sleep mode).
Take off the Kobo's back cover using a sliding tool or something like a bus card.
Notice inside there is an internal microSD card, carefully take it out and put it into a microSD card reader USB, they're very cheap I believe, if you don't have one. Do NOT substitute with a device that just accepts microSD cards, like a tablet, that will probably mess up the process or even the tablet itself! It should be a microSD card reader.
Step 2: Start USB Image Tool and then plug in the microSD card reader USB, it will show up in the software but double check it's the correct drive.
When prompted by Windows, do NOT format the microSD card when connected to the PC, because it's unnecessary, the software and backup image will do what's needed for you.
Step 3: Click the "Restore" button and select the backup image
(the .img file) and let it flash the image to the microSD card.
When finished, safely remove the microSD card reader USB and place it back into the Kobo and close the back cover.
Turn on your device. Done!
If you wanted to backup a microSD card image (.img file), you would use the "Backup" button instead of the "Restore" button.
Good luck.
