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.
Choose the Mayo flag in the character creator.
Choose the transgender pride flag.
(Do you understand?) Read an Irish annotation.
Find Colum drinking coffee.
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.
Finish ‘Opening’ chapter.
Draw for the first time.
Finish ‘The Anomaly’ chapter.
Finish ‘The Back of Beyond’ chapter.
Erase for the length of one Mass.
Finish ‘Cassiopeia was over Keel’ chapter.
Play the game in Irish.
Finish ‘Coming and Going’ chapter.
Erase for the first time.