If you want to see a show while you're in town, try and grab some tickets at Brucknerhaus Congress Centre in Innenstadt. If you enjoy the show and want to see another, Musiktheater and Linz State Theater are both not far.
You can browse the exhibits at Lentos Art Museum, a museum with a storied past, during your travels to Linz. Make time to visit the cathedral and monuments while you're in the area.