Welcome!
Here you go:
https://www.mossberg.com/products/shotguns/pump-action/mossberg-flexIt's an interesting concept.
As has been said, it's built around the proven 500 receiver and barrel(s). I've played with one a bit but don't own a Flex model.
I do own a some 500s in both 12 & 20 gauge. They are good guns, pattern well and there are a great variety of choke brands and exit diameters made to fit them, since they take Win-Choke, Accu-Choke and Invector (all the same) choke tubes.
I have some that work well for me as others do. The best and most consistent patterns I see are with Hevi-13 shells but I'm sure you'll have other recommendations as well.
Good luck to your Buddy and to you this turkey season.
Thanks,
Clark