Soldiers from the 3rd Separate Assault Brigade of the Armed Forces of Ukraine destroyed a Russian Shylka anti-aircraft gun with the help of drones. — Ukrinform.
To me it seems like WW2 style close support anti-air is idealy suited for slow flying smaller drones.
Given the low altitude, size and no armor I would think the way to go was to use even smaller calibres to increase the "bullet density". Chain fed linked 5.56 machine guns in an array perhaps?
I was reading some article that stated the effectiveness of Ukrainian anti-drone defenses had decreased because Russian drones, most notably their Shahed variants, are flying at higher altitudes.
The machine-gun type defenses don't have the altitude range to hit higher flying drones, so the interception rate went down to 80%.