This is the grey area. The search for is almost exclusively performed by users running Atmosphere or Tinfoil .
If you install an NSP of the base game without the matching update (UPD), you cannot play online via custom servers (like Lan-Play or Pretendo) and you will miss 48 tracks. switch nsp mario kart 8 deluxe upd
: Addressed specific technical issues, including a bug on the 3DS Music Park This is the grey area
Added the Master Cycle Zero and Champion's Tunic. 🏁 Game Modes switch nsp mario kart 8 deluxe upd
Even legitimate users run into issues. Here are fixes for scenarios that might drive someone to search for manual NSP/UPD files.