Season the flesh side of the salmon with the citrus zest, thyme, salt and pepper.
Remove the skin and white pith from the tangelos, oranges and grapefruits with a sharp knife. Working over a large bowl, cut between the membranes of the grapefruits to release the sections into the bowl. Squeeze the membranes to extract the juice. Slice the tangelos and oranges into rounds and add them to the bowl.
In a large nonstick skillet, heat 1 tablespoon olive oil until shimmering. Add the salmon, skin-side down, and cook over medium heat, pressing gently with a fish spatula to flatten, until the skin is browned and crisp, about 5 minutes. Flip the salmon and cook until medium, 1 to 2 minutes.
Meanwhile, add the avocado, herbs, scallions and remaining 2 tablespoons olive oil to the large bowl with the citrus. Season with salt and pepper, then gently toss to mix. Serve the salad with the crispy salmon.