Preheat your air fryer to 375°F (190°C) for a few minutes, or use the preheat button, so it's hot and ready.
In a bowl, whisk together the buttermilk, beer, and eggs until smooth.
In a second bowl, combine the flour, paprika, garlic powder, cayenne pepper, and salt. Add the Panko bread crumbs to a third bowl.
Dredge each onion ring in the seasoned flour, then dip it into the buttermilk-beer-egg mixture, and finally coat it fully in the Panko bread crumbs. Set the breaded rings on a plate.
Arrange the onion rings in a single layer in the preheated air fryer basket. Don't overcrowd — cook in batches if needed.
Air fry for 10–12 minutes, flipping halfway through, until deep golden brown and crispy. Add an extra minute or two for more crunch.
Serve immediately while hot and crisp.