Here is the full list of all 18 Quern - Undying Thoughts achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Find a secret near the Watchtower
Find a secret near the Mine
Find a secret in the Corridor underground
Draw at least 19 sketches in your notebook
Follow the Professor’s guidance
Solve the melody repeat puzzle on your first try
Open the lower part of the Crystal Lab without using blue light
Follow Gamana’s guidance
Return the professor’s most precious item to its place
Going deeper underground
Meet Gamana for the first time
Create a purified energy crystal
Get access to the tower in the Main Square
Listen to the story of the Seekers
Taste all the berry juices
Revive the plants in the Gardens
Survive the boat ride
Enter the Professor’s Crystal Lab