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