Preheat the oven to 350 degrees F. Mound the potatoes on a rimmed baking sheet. Drizzle with 1 tablespoon of the olive oil; toss to coat and spread evenly on the sheet. Bake for 20 minutes. Scatter the apples around the potatoes and bake until tender, 15 minutes more.
Meanwhile, cook the salmon according to the package directions.
Combine the ale, 3 tablespoons of the vinegar, salt, and sugar in a large skillet. Set over medium heat and bring to a boil. Add the scallions and simmer for 3 minutes. Remove from the heat and whisk in the mustard. Whisk in the remaining 3 tablespoons olive oil and 2 tablespoons vinegar until blended.
Add the potato mixture and parsley to the skillet; toss to coat. Serve with the salmon.