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.
Finish ‘Cassiopeia was over Keel’ chapter.
Finish ‘Coming and Going’ chapter.
(Do you understand?) Read an Irish annotation.
Find Colum drinking coffee.
Erase for the first time.
Play the game in Irish.
Finish ‘The Back of Beyond’ chapter.
Finish ‘The Anomaly’ chapter.
Finish ‘Opening’ chapter.
Choose the transgender pride flag.
Choose the Mayo flag in the character creator.
After finishing the first chapter, go to the last chapter.
(That we may live to see this time next year.) Write every diary entry in Opening.
Erase for the length of one Mass.
Draw for the first time.