XCI files are actually inspired by the Commodore 64's disk image format but have been repurposed and are commonly used in the context of Nintendo Switch game distribution. XCI files essentially act as a container for Switch game data, often used for backups or transfers. However, the use of XCI files can be controversial as it relates to game piracy.
Which of those would you like?
Here is a look into what these files are, why the "fixed" versions exist, and what’s actually happening behind the scenes of Zelda's first solo mainline adventure. Decoding the Terms: NSP, XCI, and "Fixed"
Brief summary of the paper’s argument about how Echoes of Wisdom reinterprets Zelda’s role and puzzle mechanics.