The trailing likely refers to "eShop" or "encrypted" — in homebrew circles, you’ll see "e" used to denote the original decrypted eShop dump (as opposed to a cartridge dump).
The 3DS port of Rebirth is often cited as the most "unstable" version compared to PC or Switch versions. The Binding of Isaac: Rebirth - hShop the binding of isaac rebirth decrypted 3ds e
The version of The Binding of Isaac: Rebirth for the Nintendo 3DS refers to a file format (typically .3ds or .cia ) that has had its digital rights management (DRM) removed, making it playable on handheld emulators like Citra or for modding on Homebrew-enabled systems. The trailing likely refers to "eShop" or "encrypted"
