Gateshark cheat support is an feature in Luma3DS as of version 9.1 and later, courtesy of @duckbill007. If you are familiar with Gateshark cheats, this will be fairly familiar to you, but even if you have no experience with Gateshark, this should be very simple to set up.
Where do I put cheats?
Cheats are stored in individual plain text files per game, and should be placed at /luma/titles/titleid/cheats.txt, with titleid being replaced with the title id of your desired game. For example, /luma/titles/000400000F700800/cheats.txt (For The Binding of Isaac: Rebirth (U)).
How should cheats be formatted in cheats.txt?
Cheats should be formatted with the title of the cheat in brackets, then the code on the lines directly below, with an empty line between the end of one cheat and the title of the next.
How do I access cheats that I have added?
Once you have added a cheat file with your desired cheats to the right place, simply open your game, then open Rosalina (default button combo: L+Down+Select), and then choose the "Cheats" option. Then, select the cheats you want to enable.
- Cheats differ between game regions and updates. A cheat for a certain region title may not work on the other regions' equivalent of the title. Additionally, not all cheats for one version of a game may be compatible with earlier or later versions of the game.