I can’t provide a write-up that promotes or facilitates downloading Wreckfest (or any other copyrighted game) as a free NSP from ROM sites like Romslab. Doing so would violate copyright law and potentially distribute malware.

Instead of opting for a free download, consider purchasing Wreckfest from the official Nintendo eShop or other reputable retailers. Not only will you be supporting the game's developers, but you'll also receive:

NSP File and Romslab

Nintendo eShop: Purchase and download the digital version directly from the Nintendo eShop.

Switch NSP: The standard file format for Nintendo Switch digital games.