I’m trying to understand the SD part of the Ethernet2 shield. Do I use the generic SD library or is it part of the Ethernet2 library? Does the SD card need to be formatted a special way?
SD is just going along for the ride, and has nothing to do with ethernet. Use the SD library. Format card in the kosher manner. Details are at the head of the storage forum.
do not use the Ethernet2 library. the new Ethernet library is for W5500 too