Here is the full list of all 9 Maui achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Fulfill your kuleana
Gain the favor of Lono
Gain the favor of Kanaloa
Find a strange island
Gain the favor of Ku
Enter the Halau for the first time
Plant your first taro
Gain the favor of Kane
Defeat your first enemy