There appears to be very little recoil.

They don't say what gauge they're firing, which would be a factor. Might be less than 12-gauge.

If you figure that weight of the gun is going to cut into flight time, you might want a light gun if possible.

EDIT: The video here shows Ukrainian soldiers testing shotguns against drones. The guy says that #3 buckshot is inadequate to break the blades:

https://www.twz.com/land/anti-drone-weapon-with-24-barrels-firing-buckshot-like-rounds-emerges-on-russian-buggies

So there may be some lower bounds on what they can effectively use. It looks like there are double-aught .410 shells, but I'd guess that you wouldn't be sending many balls downrange.

EDIT2: I was wondering about using a 40mm underbarrel grenade launcher firing flechette rounds earlier, as that'd let everyone in a squad carry something that'd have at least one round that'd put a lot of projectiles downrange quickly; one has to assume that a squad patrolling isn't going to give up their assault rifles for shotguns or similar. NATO does have a 40mm canister round.