Aaargh, you know, the last time I was tinkering around with handheld devices in this way was prior to the invention of the iPhone, when I kept "flashing the ROMs" of my Windows-based cellphones.
That was Windows Mobile, or whatever it was called back in those days – an utter nightmare, and I'd hate to go back to any of that.
If there were easy-to-follow instructions for accomplishing with my ancient Kobo Mini what you accomplished with yours, I might give it a try. But I'm just too busy to scrutinize any of this in detail.
Besides, in my case, a battery purchase and swap would be necessary, too, and I'd definitely not attempt to swap the battery on my own. A technician's assistance would be needed.
(I've now re-checked the battery level on my Kobo Mini: it's now down to 10%, despite my not having used it at all since it last showed 87% a couple of days ago. So, this particular battery has run its course...)