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