An Apple TV tried to AirDrop me a system diagnosis archive. What happened?
The Apple TV supports creating sysdiagnose bundles and sending them over AirDrop. Apple staff recommend this regularly on the Apple Developer Forums.


  To capture a sysdiagnose, hold down the Play/Pause and - buttons on the Apple TV Remote for six seconds, until you see a dialog confirmation on-screen.  From there, follow the instructions to AirDrop the sysdiagnose off the device.


Beta 7 crashes on HDMI hotplug - Apple Developer Forums

It's possible something's accidentally held down the buttons on the Apple TV remote (since they are next to each other) which has caused this action.

AirDrop must be a fairly new feature for the sysdiagnose functionality since the guide for creating a sysdiagnose from an Apple TV on the Apple Developer site still says a USB-A to USB-C cable and iTunes are required: Apple TV sysdiagnose Logging Instructions (link behind developer login).