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