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.
Complete all chapters
Complete chapter 16
Fully upgrade the sling
Find Rodric's forge
Complete chapter 15
Fully upgrade the equipment
Complete chapter 14
Complete chapter 13
Complete chapter 12
Craft 100 ammunitions
Complete chapter 11
Complete chapter 10
Find 6 flowers
Complete chapter 9
Find 13 curiosities
Complete chapter 8
Find the tomb
Complete chapter 7
Complete chapter 6
Complete chapter 5
Complete chapter 4
Complete chapter 3
Complete chapter 2
Find a lunch for Hugo
Complete chapter 1
Complete the aiming training
Find all the flowers
Find all curiosities
Find all the gifts for the orphans
Enter into the 5 alchemist carts
Play hide-and-seek
Save a soldier
Enter through the main door
Save the dying
Stay with the captain