First generation Kobo doesn't seem to have an internal SD-Card but rather a Samsung flash memory component: see
https://www.mobileread.com/forums/showthread.php?t=83612
This being said, when I plug it to USB, it opens a drive with an architecture that seems very similar to the Kobo WiFi, including the .kobo folder... Too bad I cannot run any command, like "fbset" to learn more about it.