I need to answer in public, except sharing this one niche, so I will give examples here.
Anyway, even my course focus on fake things, I still think they are "halal" because people are not loosing money, only time getting sometimes.
Because getting "free game", "free currency in game", "free movies" is worse. So you are giving a lesson to people to not trust such things. Win-win

It depends how you look at this
Anyway, legit examples can be used by anyone:
-instruction how to jailbreak iphone
-instruction how to root android phone, for example Nokia 5.1
-legit currency in game, just set up $5-$10 offers in conversion, buy some currency in game and send to users, halal
-real games from Google Play or Appstore, same like currency, buy and send, gift cards to appstores, etc.
-steam cheap games, there are many games <$5, buy them, give them to customers
-make giveaways, for example if game cost $20-$50, then make a giveaway for your users and for example if you get 500 conversions, make a giveaway
There are many ways to make it legit, but I am not focusing on them. If you want, you can find or create many niches.
In my course, you will find mostly not legit niches, that are not giving anything to user, I have few legit niches from above and that's all.
If you want to make legit niche that brings value to user, all depends to you and your calculations.
Many of my course members are doing legit niches, but I cannot reveal their niches