With the force ballista, you make a ranged spell attack. If an opponent is within 5 ft of the articifer, do you have disadvantage on that attack? What if the opponent is within 5 ft of the ballista? PHB pg 195, "…you have disadvantage on the attack roll if you are within 5 feet of a hostile creature who can see you and who isn't incapacitated."

You're making the attack roll, it matters if enemies are next to you.

— Dan Dillon 👥 (@Dan_Dillon_1) January 25, 2020