Preheat your air fryer to 400°F (200°C).
Slice the russet potato into even wedges and pat them thoroughly dry with a paper towel.
In a small bowl, toss the potato wedges with avocado oil and a pinch of sea salt.
Place the potatoes in the air fryer basket in a single layer and cook for 15 minutes, shaking the basket halfway through.
While the potatoes cook, whisk together the flour, light beer, garlic powder, and paprika in a shallow dish until a smooth batter forms.
Pat the cod fillet dry, season with the remaining salt and pepper, and dip into the beer batter to coat evenly.
Open the air fryer, move the potatoes to one side, and place the battered cod on the other side (use a small piece of parchment paper under the fish if needed).
Air fry everything for an additional 8 to 10 minutes until the fish is opaque and the coating is crisp and golden.
Serve immediately while hot for the best texture.