Never got a notification in the region I found them and for most time no notification at all.
Think I only seen a notification like that 3-4 times from latest 2020 patch and 2 or 3 was in South coast when I /We where somewhere els and once from Forest region.
I may have found 20-ish just laying so far and once even a Reaper without any notification in same session. Not even sure if they are rivals, loot is so scattered around nowadays.
Once we fast traveled down to South coast after that notification saying a machine got killed by a player and even found it, a harvester with rival loot because I got a schematic from it.
That one we guess had fallen from high cliffs above laying in the water’s edge just on that underwater edge that make you fall forever and drown. This was somewhere on southside of south coast near one of the forts. But I believe that may have to do with how machines is programmed to move and where. Seen plain hunters walking out in the water’s edge in Källby(?) in that bay in South coast and die from shortcuts or falling over that underwater edge. Where they before used to run around they bay in town streets to get you.
I’m still looking to find one more while recording it. So far I found another bug that I have to report where living hunters just disappear while the fight is ongoing.