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