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