qt.bluetooth: Dummy backend running. Qt Bluetooth module is non-functional

[probonopd]

On FreeBSD 31.0-RELEASE I can build BlueMoon but when I run it on the command line it prints

FreeBSD% ./blue_moon                      
qt.bluetooth: Dummy backend running. Qt Bluetooth module is non-functional.

qt5-connectivity-5.15.2_1 is installed.

How can this be solved?