adwaita-qt software package provides Qt 5 port of GNOME?s Adwaita theme, 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 adwaita-qt
adwaita-qt is installed in your system.
Make ensure the adwaita-qt package were installed using the commands given below,
$ sudo dpkg-query -l | grep adwaita-qt *
You will get with adwaita-qt package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | GNOME |
| Package | adwaita-qt |
| Version | 0.5-1 |
| Description | Qt 5 port of GNOME?s Adwaita theme |
| Sub Section | gnome |