“I wonder if this was counter-battery or random target acquisition?”
UA had a drone overhead. So I assume it was artillery corrected by the drone.
Watching the video, it appears to be artillery corrected by the drone.
I'm wondering if the drone was a General Atomics MQ-1C Gray Eagle.
My guess is that the Russian 2S5 Giatsint-S 152mm self propelled gun fired some rounds and then rapidly moved to what it thought was a safe location. UA counter battery radars sent the 2S5 Giatsint-S firing location to the drone and the drone was able to locate and follow the 2S5 Giatsint-S to its "safe" location.
Once the 2S5 Giatsint-S parked, the UA must have had artillery already in position to take it out. So they took it out with drone corrected artillery.
Regardless of how UA initially located the 2S5 Giatsint-S this is bad news for Russia.