BLE AdvertisementData returns empty []

oh in the test data ino there is no functional data, so no worries about that.
I am now going back to the compass project. ( sailboat) I used with the need to connect, now I can do without that. And get the power down to the minimum possible.

There are other projects for this in my mind.

I am amazed how many ble devices are found, as it is supposed to be for short range comms.

Depends on the definition of short range. BLE's main problem is obstacles - anything between the devices may cause a signal loss.