To make the dressing, add the balsamic, maple, olive oil, and salt to a small bowl or dressing shaker and whisk or shake until combined. Set aside. Alternatively, you can omit this dressing recipe and use plain balsamic vinegar or drizzle the salad with balsamic glaze, if you wish.
Roughly chop the bacon and cook according to package instructions; set aside.
Keep the same pan you cooked the bacon in over medium heat, add half of the spinach, drizzle with half of the dressing, and quickly toss to warm the spinach. Remove from the heat and add the remaining spinach and toss to combine.
Divide the spinach between bowls or plates. Top each with strawberries, bacon, and walnuts. If using red onion, use the desired amount and add here; a little goes a long way.
Drizzle with remaining dressing, if desired, and sprinkle with vegan feta and black pepper.