Have you first tried FlyJb X ?
If you open the game, and enable FlyJb after its useless since the game will store that you are Jailbreak.
Steps :
1) Delete the game.
2) Re install it BUT DON'T OPEN IT
3) Open FlyJb and from there, enable ur app. you can use A-bypass if you want, i use FlyJB but use any good alternatives.
4) Open your game
If that didn't work, you probably need to work with DnSpy...
Afaik you can't NOP a class, try to look functions / methods, maybe bool functions store if you are jailbreak or no.
You can also search for function names containing "jailbreak", "root".
I think the first method should work tbh, but if not good luck for the second one, it's gonna be a lot of work to test them