Here is the full list of all 21 Jusant achievements. It takes around 5-6 hours to unlock all of the achievements on Windows.
Turn all altars.
Listen to all shells.
Hug the ballast 20 times.
Warm up the ballast in chapter 6.
Complete all cairns.
Activate all frescos.
Read all letters.
Complete the game.
Use the echo on a frozen ballast in Chapter 6.
Read all of Bianca's journal entries.
Place a piton at the top of a wall run.
Restore your stamina more than 50 times while climbing.
Complete more than 200 jumps or double jumps in one game.
Stop 25 pebbles with a single echo from the ballast.
Turn an altar.
Scare more than 10 chocos back to their burrow.
Hug the ballast.
Activate a fresco.
Complete a cairn.
Listen to a shell.
Read a letter.