On the off-chance this is possible, can you set up a different wifi names (SSIDs) in your router? Perhaps different virtual networks or just by separating the bands? Or, possibly just use a Guest network on the router for the Kobo? Not a solution, but might be a good workaround.
BTW, usually I see the advice to keep IOT devices on their own virtual network so they don't leak/steal information from your network of meaningful devices (i.e., computers, NAS, etc.). So, doing the above (if possible) could be the first step on that journey
.