Is there any debug possibility
From the code : ble_trace0 - ble_trace6 used to log the prints but it is defined dummy in bleapp.h
Is that legacy code ?
Unfortunately there is not as the HCI UART Rx line is not accessible via a switch the way it is on the full featured TAG3 development board. On the TAG3 board, SW4 can be configured and the trace plugin within the IDE is then functional.