These are "Nintendo Submission Packages," usually used for digital eShop titles, updates, or DLC. The Legal Method: Dumping Your Own Games
"ISO" is a general term often used by newcomers, but Switch emulation specifically uses the following file types:
The only legally defensible way to obtain game files for use with an emulator is to "dump" them from a physical console you own.
These are "Game Cartridge" dumps, typically containing the full base game.
The official distribution and development of the ceased on March 4, 2024, following a $2.4 million settlement between its parent company, Tropic Haze LLC, and Nintendo. As part of this legal agreement, the official Yuzu website and its source code repositories were permanently taken down.
While the original project is no longer updated, users seeking to run "Yuzu ISOs" (more commonly found in or XCI formats) must now rely on archived builds or community forks. Understanding Yuzu Game Formats