I tried with koreader-kobo-arm-linux-gnueabihf-v2015.11-11-g16509e2 and the 3.13.1 pack (which seems ok to me). Will try again this afternoon
Got it working.
But the loader screen did not display correctly (just got some fuzzy lines on the screen with no images at all to press), so I have to tap blindly on the screen to load one or the other reader software...