To install Monster Hunter Rise updates and DLC on a modded Nintendo Switch, you must treat the base game, update, and DLC files as individual Core Installation Tools
You cannot simply drag and drop files onto a stock Nintendo Switch. You need the following: monster hunter rise switch nsp update dlc install
to drag and drop the files directly into the "SD Card Install" or "NAND Install" folders. To install Monster Hunter Rise updates and DLC
These tools allow for installation from an SD card or via USB using a loader on your PC. Nintendo Switch NSP Combination Install Tutorial you must treat the base game
Here’s a concise technical report on installing Monster Hunter Rise (NSP), updates, and DLC on a (custom firmware / atmosphere).