averiguar is more "to figure out", like a detective figuring out who the murderer was by examining the evidence. But it's a pretty subtle distinction and the meaning pretty much overlaps with "to find out."
DL offers possible translations only and "found" is fine as a possible translation of "discubierto". They had discovered/found a new island. He had discovered/found a flaw. She had discovered/found a cure, etc.
The hints are not always right. I think that is done on purpose so we will get out of the habit of relying on them so much and rely more on memory and do the necessary external research on usage rules. That is my guess, anyway.