The note in the rules for explorers and pirates states that "settlements may not be built on intersections adjacent to undiscovered hexes." I am new to this expansion, does this mean that no undiscovered hex can be within two 'road lengths' of a settlement like the distance rule for settlements in base Catan?
An intersection is formed at the point where three hexes meet. The intersection is hence adjacent to these three hexes. A settlement cannot be built if any of these three hexes is as yet undiscovered. The rule means nothing else, hence a settlement can definitely be built closer to an undiscovered hex than two road lengths away; it just has to be at least one road length away.