I do. I started cooking when I was 6. My first dish was blackberry pancakes from a recipe in the Times Picayune Creole Cook Book. Been cooking and developing recipes from that book ever since and learn a fair amount from those 3 aforementioned Cajun chefs as well.
Well you can do anything you like. I guess you could call duck seafood. lol. I usually keep my gumbos mixes to those that breathe air and those that breathe underwater, i.e. I'd do a duck and andouille gumbo but I'd use shrimp with other seafood. But that's just me.
Really, any gumbo ought to have a nice dark roux, at least the color of caramel. Good luck!
BTW, when my dad had to go on the Atkins diet and my mother could no longer use fat to make a roux, she simply roasted the flour in the oven, stirring it occasionally until it reached the required color. So if you have health issues, this might be fix for you.