bluedevil software package provides KDE Bluetooth stack, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install bluedevil
bluedevil is installed in your system.
Make ensure the bluedevil package were installed using the commands given below,
$ sudo dpkg-query -l | grep bluedevil *
You will get with bluedevil package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Network |
| Package | bluedevil |
| Version | 4:5.8.2-1 |
| Description | KDE Bluetooth stack |
| Sub Section | Net |