M - Rkb-(usa)-nswtch-nsp-update190-ziperto.rar

If you are looking for the "features" included in this specific RAR file, they are the official additions made by Nintendo in the v1.9.0 patch:

: The .rar extension means the file is compressed. You must extract it (using WinRAR or 7-Zip) to find the .nsp file inside, which is the actual update package used by Switch emulators (like Yuzu or Ryujinx) or hacked consoles. M RKB-(USA)-NSwTcH-NSP-UPDATE190-Ziperto.rar

: Added eight tracks, including the new Squeaky Clean Sprint and returning classics like Wii Koopa Cape and GCN Daisy Cruiser . System Improvements : If you are looking for the "features" included

Specifically, "UPDATE190" indicates this is the , which was released in July 2023 to add support for Wave 5 of the Booster Course Pass DLC. Key Features of this Update (v1.9.0) System Improvements : Specifically

The filename refers to a pirated update file for the game Mario Kart 8 Deluxe on the Nintendo Switch .