Thanks for your answer, @Hayato213 .
The first step of the link that you sent is to creat an emuNand, but once my Switch is already with that error, it doesn't restrain me to use it to create an emunand?
The exactly same thing happened to me and I didn't found any way to fix the sysNand.
I've bought the Switch with Atmos already in too, and don't know if it's using donor nand.
@Hayato213, there's a way to discover this?