In a medium saucepan over medium heat, bring broth to a boil. Stir in couscous, red pepper, and ¼ teaspoon salt, then cover and remove from heat. Let sit, covered, 10 minutes, then fluff with a fork and transfer to a medium bowl.
Meanwhile, in a large bowl, whisk oil, lemon zest, lemon juice, mustard, and ¼ teaspoon salt until combined. Add couscous, chickpeas, cucumber, bell pepper, feta, almonds, mint, tomatoes, and onion and toss to combine. Serve warm or chilled.
