As Nintendo moves further away from the 3DS era, the responsibility of keeping games like Super Mystery Dungeon alive falls to archivists and responsible homebrew enthusiasts. Just remember: if you love the game, support the franchise. Buy a physical copy if you can find one, and always dump your own files when possible.
format is the standard for installing game data directly to the SD card. pokemon super mystery dungeon story/gameplay retrospection Pokemon Super Mystery Dungeon -USA-.cia
For detailed step-by-step guides, refer to these comprehensive community resources: Pokemon Super Mystery Dungeon - Guide and Walkthrough 22 Feb 2016 — As Nintendo moves further away from the 3DS