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