Here is the full list of all 39 Spiritfarer achievements. It takes around 35-40 hours to unlock all of the achievements on Windows.
Accomplish your very last objective
Bring all releasable spirits to the Everdoor
Shear sheeps at least 50 times
Collect all figureheads
Activate all the shrines
Complete all collections
Discover all recipes
Fully improve Elena's Cubicle
Use Alex's bus stops 50 times
Light up all Lighthouses
Build all houses and stations at least once on the boat
Fully improve Buck's Lair of Wonders
Make all spirits reach the ecstatic mood at least once
Complete thirty errands for Francis
Have your final conversation with Hades
Unsubscribe from Feedorama
Fully improve Atul's Workshop
Fully improve Stanley's Playroom
Fully improve Bruce and Mickey's Crib
Fully improve Gustav's Gallery
Have your second conversation with Hades
Tell Astrid about Giovanni's night excursions
Do not tell Astrid about Giovanni's night excursions
Fully improve Astrid's Bungalow
Endure 10 of Albert's jokes
Sell at least 200 items
Sign up to Feedorama
Give a dating advice
Find and shelter all sheeps
Complete twelve errands for Francis
Fully improve Alice's Cottage
Make 5 spirits reach the ecstatic mood at least once
Fully improve Summer's Sanctuary
Have your first conversation with Hades
Fully improve Gwen's Lodge
Buy at least 100 items from Raccoon Inc
Complete one errand for Francis
Give Furogawa Tour's guide a tip
Make one spirit reach the ecstatic mood at least once