Heat oil in a large frying pan or tabletop fryer to 365°F.
In a large bowl, whisk up flour with Old Bay, chili powder, garlic powder, salt and pepper. Whisk beer into batter then add egg and combine. Dunk fish pieces into batter and fry a few pieces at a time to deep golden brown. Salt fish when they come out of the oil, while they’re still hot. Keep warm in a moderate oven on a wire rack set on a rimmed baking sheet.
Char tortillas in hot, dry skillet or over a burner flame.
In a food processor or blender, combine chipotles in adobo, lime juice, salt and crema until smooth; transfer to a small bowl.
Combine onion, jalapeño, salt, tomatoes and cilantro then fold in diced avocado and add lemon or lime juice.
Serve fish with tortillas and fixins alongside.