Connect your Switch to a PC via USB and use the mode in DBI . This allows you to simply drag and drop NSP files from your PC into a virtual "Install" folder on the Switch . Tinfoil (Network/Shop Method) :
Understanding NSP Files: The Digital Standard for Nintendo Switch nsp file
. In this environment, NSP-related files are used for cross-domain network management and automation. Connect your Switch to a PC via USB and use the mode in DBI