I actually also own a kobo and have been running KOReader on it for a couple years now, but my memory is that when I first got it I booted it up and it requested to be connected to the internet, then wouldn't allow me to progress without logging in through a 3rd party (there were many offered, walmart.com was the first option listed). I remember having to do something weird to bypass that (removing a .db file I believe after connecting via commandline?), and then ending up in a state where I don't need to connect to some company's cloud login but I also can never connect this device to wifi, ever, or it will do that again.
Are they more open these days?
https://old.reddit.com/r/kobo/comments/mt2f30/how_to_bypass_...
Connecting it to wifi afterwards isn't a problem, to tbe best of my knowledge.
Firmware downloads: https://pgaskin.net/KoboStuff/kobofirmware.html
non-obvious but you just use it like a usb device ereader when you receive it:
- connect to computer with usb-c
- mount as usb drive
- edit .kobo/Kobo/Kobo eReader.conf adding SideloadedMode=true
- remove .kobo/KoboReader.sqlite
- reboot, then just use kobo as usb drive from then on, no account necessary
got one and use it more than my remarkable because it has a backlight for indoors (in addition to e-ink for outdoors)
A few months ago, I attempted to do install KOReader on a kindle, and the experience is definitely not for the faint of heart. Plus, I can't use the wireless capabilities for the reason you mentioned. It was (one) of the reason I wanted to install KOReader in the first place, but live and learn.