Using NSP files outside of the official eShop ecosystem carries significant risks that every user should be aware of:
As mentioned, these represent eShop content. They are "installed" to the console’s NAND (internal memory) or SD card. switch nsp
One area of interest for homebrew developers and enthusiasts was the NSP file format. NSP files are used by Nintendo to package and distribute games, demos, and other content on the Switch. These files contain the game's assets, code, and metadata, all compressed and encrypted. Using NSP files outside of the official eShop