Sony so much doesn't support older products that they removed all existing downloads.
Almost the oldest Kobos still get good firmware updates:
https://pgaskin.net/KoboStuff/kobofirmware.html
I think some have even run Kobo Glo FW on the Kobo Mini?
I've had maybe nine makes of ereader inc Sony, reMarkable, four Kindle models (tested 3 others), six Kobo models.
I find Kobo the best and better than the average retail gadget.
You've had one unfortunate experience that's not representative.