Here is the full list of all 31 Yoku's Island Express achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Discover the heart cluster at the bottom of the sea
Collect every ability upgrade
Complete Rinri's quest
Activate all Scarabs
Hatch the God Egg
Collect all Wickerlings
Unlock all treasure chests
Complete Thorn quest
Try every ball style
Complete Willo's quest
Complete the story
Become the Postmaster
Defeat the Spider
Get the biggest wallet
Deliver the cake to the inventors house
Discover Fosfor’s Lair
Defeat Screetch
Befriend a Sootling
Unlock all the Beelines
Complete the temple trials
Customise Yoku’s ball
Take the surviving egg to Dipperloaf
Save Spina
Collect the Divefish
Ride the Beeline
Toot the noisemaker 1000 times
Suck up a slug with the Slug Vacuum
Find the Post-office
Free Kickback
Toot the noisemaker 100 times
Blow the noisemaker