You're looking for this untapped niche because you're looking for easy money.
You're never going to find it. If there's profit, there's competitors.
You can be the King of the niche: "How to prevent forest fires in the Desert"
And you're not going to make much.
Just pick a niche, find a problem in which people are are willing to pay for the solution!
If you find a huge pain in the massively competitive make money online niche
Then solve it and get paid!
Dont just limit yourself to blogs/info products.