A new save file won't work if you are missing the game updates.
Smash Ultimate Update 13.0.1.nsp.nsp files.If you see "Save data is corrupted" on launch, your game version doesn’t match the save file’s version. save data super smash bros ultimate yuzu new
save_data.dat with your backup.In newer Yuzu builds, this setting causes save corruption on launch for Smash. Paper: Saving Super Smash Bros
Backing up and restoring SSBU saves on Yuzu is straightforward: locate the title save folder, copy it while Yuzu is closed, and restore when needed. For transfers between real Switch and Yuzu, use proper dumping tools and respect legal constraints. Regular backups and versioned archives reduce risk of irreversible data loss. Go to Yuzu > File > Install Files to NAND