Preheat your air fryer to 400°F (200°C).
Cut the Russet potato into even wedges. In a bowl, toss them with the avocado oil and half of the sea salt, black pepper, and paprika.
Place the potato wedges in the air fryer basket in a single layer and cook for 15-18 minutes, shaking halfway through, until crispy and golden.
While the potatoes cook, prepare the batter by whisking together the flour, cornstarch, garlic powder, and the remaining salt, pepper, and paprika in a shallow bowl.
Whisk the egg white and light beer into the dry ingredients until a smooth, thin batter forms.
Pat the cod fillet completely dry with paper towels. Dip the fish into the batter, ensuring it is fully coated.
Once the potatoes are done, remove them and keep warm. Lightly grease the air fryer basket and place the battered fish inside.
Air fry the fish at 375°F (190°C) for 10-12 minutes, flipping carefully halfway through, until the coating is crispy and the fish flakes easily with a fork.
Serve the crispy fish alongside the potato wedges immediately.