What is debug mode?
Enabling Nearby debug mode on a device allows that device to receive debug mode Nearby Notifications attachments. Debug mode also enables more detailed bug reports, which may help when troubleshooting.
How do I turn on debug mode on device?
First, enable Android developer options. Then, open Google Settings and select Nearby. Finally, tap on the gear icon and enable the "Include debug results" entry.
How do I use debug attachments / how do I test my attachments?
When creating the attachment with Beacon Dashboard, if you toggle the "Production mode" switch to "Debug mode", the attachment/notification will only appear for devices that have Discovery Debug mode turned on.
See Obtain and configure beacons to learn more.