Heat the olive oil in a large skillet over medium heat. Add the diced onion and cook for 3–5 minutes, until softened.
Add the ground beef and cook, breaking it up as it browns, for 7–10 minutes. Drain off any excess grease if needed.
Stir in the tomato sauce, mustard, ketchup, BBQ sauce, and salt. Lower the heat and let it simmer for 3–5 minutes, until thickened.
Preheat the oven to 400°F and line a 9×13-inch baking sheet with parchment paper.
Spread the tortilla chips out in an even layer, then spoon the sloppy joe mixture over the top.
Sprinkle the shredded cheddar evenly over everything.
Bake uncovered for 7–10 minutes, just until the cheese is melted and bubbly.
Remove from the oven and finish with chopped pickles, sour cream, and green onions. Serve right away and dig in.