Here is the full list of all 15 If Found... achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
After finishing the first chapter, go to the last chapter.
Erase for the length of one Mass.
Play the game in Irish.
Choose the transgender pride flag.
Choose the Mayo flag in the character creator.
Finish ‘Opening’ chapter.
(That we may live to see this time next year.) Write every diary entry in Opening.
Find Colum drinking coffee.
Draw for the first time.
Finish ‘The Back of Beyond’ chapter.
Finish ‘The Anomaly’ chapter.
(Do you understand?) Read an Irish annotation.
Finish ‘Cassiopeia was over Keel’ chapter.
Finish ‘Coming and Going’ chapter.
Erase for the first time.