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
Give a dating advice
Use Alex's bus stops 50 times
Complete all collections
Activate all the shrines
Unsubscribe from Feedorama
Discover all recipes
Bring all releasable spirits to the Everdoor
Have your final conversation with Hades
Collect all figureheads
Endure 10 of Albert's jokes
Light up all Lighthouses
Shear sheeps at least 50 times
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
Have your second conversation with Hades
Fully improve Gustav's Gallery
Sign up to Feedorama
Tell Astrid about Giovanni's night excursions
Do not tell Astrid about Giovanni's night excursions
Fully improve Astrid's Bungalow
Fully improve Bruce and Mickey's Crib
Complete thirty errands for Francis
Fully improve Atul's Workshop
Find and shelter all sheeps
Fully improve Stanley's Playroom
Make 5 spirits reach the ecstatic mood at least once
Complete twelve errands for Francis
Sell at least 200 items
Buy at least 100 items from Raccoon Inc
Fully improve Alice's Cottage
Have your first conversation with Hades
Fully improve Summer's Sanctuary
Fully improve Gwen's Lodge
Give Furogawa Tour's guide a tip
Complete one errand for Francis
Make one spirit reach the ecstatic mood at least once