To unlock the "Small Town Blues" trophy in Life is Strange 2 - Episode 2: Rules, you need to find the sixth and final optional collectible in Claire and Stephen's house.
After returning from the Christmas Market, the boys enter Karen's room. At the far side of the room is a CD Player.
To the left of the CD Player is a CD Rack, and to the left of that is a Socket. Put the plug in the socket, and then Play the CD Player. To find out why it isn't working, Sean opens up the lid and finds a train ticket inside, the final collectible.