Great question — answering as the UphillTech team:
You are not going to reproduce deep frying with any alternative. Certainly steaming will not get you in the ball park (generally because you are adding moisture). "Air frying" (really convection baking) can get you to crispy...and you might achieve deliciousness, but it is not the same as deep frying. That may be fine for your purposes. I would suggest trying an air fryer to see if it meets your needs. Dedicated deep fryers do indeed retain a "cold zone" below the heating element so that bits of food can sink to the bottom and remain unburned. That needs to be filtered periodically and, as you mention, one would need to dispose of and change the oil as necessary.
Full answer by moscafj: https://cooking.stackexchange.com/a/128814 (CC BY-SA 4.0).
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