I don't believe that there is any way of knowing about possible First Nations issues in advance.
I believe that the best way to find out is generally to have a junior spend X millions of shareholder's dollars exploring and developing the property , and only once the junior has developed it to the 43-101 or pre-feasability stage, secured a senior partner, and otherwised aligned all of its other ducks in order , only then would any and all parties within 100km of the property in question come out of the woodwork and make claims on the deposit and all waterways, land and air routes within 200km. I think that is how the process generally works in Canada? ..
Cheers,
Luker