Yes, the internal hardware is different. The image from one will not work on the other. To fix that, you will need an image for the original device. That is available if you didn't make one or use a different card.
There is a reasonable chance the firmware is still on the Kobo server. Finding the link is what would be needed. I'm sure it has been posted, but, can't find it now. I thought it might be in
https://www.mobileread.com/forums/sh...d.php?t=221072, but, it isn't in the first few pages.
Of course, the Kobo desktop application might still update it. I don't remember exactly what Kobo said about this for the WiFi when they announced they were withdrawing support.