Here is the full list of all 35 A Plague Tale: Innocence achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Find all the flowers
Enter into the 5 alchemist carts
Enter through the main door
Find all curiosities
Find all the gifts for the orphans
Complete all chapters
Complete chapter 16
Find Rodric's forge
Complete chapter 15
Fully upgrade the sling
Complete chapter 14
Stay with the captain
Complete chapter 13
Complete chapter 12
Craft 100 ammunitions
Save the dying
Complete chapter 11
Complete chapter 10
Find 6 flowers
Fully upgrade the equipment
Complete chapter 9
Complete chapter 8
Find the tomb
Find 13 curiosities
Complete chapter 7
Complete chapter 6
Complete chapter 5
Save a soldier
Complete chapter 4
Play hide-and-seek
Complete chapter 3
Complete chapter 2
Find a lunch for Hugo
Complete chapter 1
Complete the aiming training