La solution était toute simple !
Il suffit en fait de renommer le dossier nintendo en emutendo .
C'est une manip à faire depuis sx os 2.3 bêta pour l'ancienne emunand .
Tout est expliquer dans la news du sx os 2.3 :
"The 'Emutendo' folder
In addition to the new microSD emuNAND system we also introduce the 'Emutendo' folder on your microSD card. As you've probably noticed, the Switch saves various data to a 'Nintendo' folder on your microSD card. To completely decouple this data between your Original Firmware and your EmuNAND enabled firmware we have made EmuNAND enabled systems use this differently named folder. If you want keep using your old SD card data with your emuNAND, simply copy/rename the 'Nintendo' folder to 'Emutendo'."
Tu peux ensuite mettre l'emunand en 6.2 via choixdujournx , et tout fonctionne parfaitement !