If using Wood r4:
Download this https://gbatemp.net/threads/deadskullzjrs-flashcart-cheat-databases.488711/
Extract Usrcheat.dat
Copy Usrcheat.dat to the flashcart _rpg/cheats folder
Done
After that just press 'Y' while selecting a game and 'X' for cheats.
Hope that helps, this is for wood...
https://github.com/AuroraWright/Luma3DS/wiki/Optional-features
Take a look at the "Locale Emulation" section
Edit: Okay, that may not work with this game, check this instead: https://gbatemp.net/threads/how-to-play-pokemon-super-mystery-dungeon-in-your-native-language-fr-de-it-es.403814/
Lol I'm stupid, for some reason I read "Wild Pokemon Shiny" instead of "Wild Pokemon encounters" all the time. Sorry again.
The only thing you can do for now is use repel.
Ahhhhh, Ok. I did not understand you well, sorry then.
For now (as far as I know) there is no option to never find a shiny pokemon or to gain 0 experience in the battles
Edit: You can request it here https://gbatemp.net/threads/pokémon-moon-gateshark-ntr-request.447851/
Hmm, If you have the green flash on the top screen when you start the game with NTR then you should be able to access the cheats menu by pressing select.
Your plugins in SD should be as follows:
If it's pkm sun:
SD:\plugin\0004000000164800\0004000000164800.plg
If it's pkm moon...
Make sure you have WiFi OFF and just one file in the 0004000000164800/0004000000175E00 folder.
If you are using luma, do you have the settings in Clock + L2?
If that is the case ... start NTR, press X + Y and in the CPU Clock menu select 804Mhz, L2 Enabled and try to start the game again.