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