Unsolved Keyboard write on console instead of in the application

[Mark81]

Qt5.9.2, Raspbian Stretch Lite for RPi3B+. I wrote a Qt5 application (no QML) with some widgets.
When I press a key on the keyboard it "writes" on the console behind the Qt application.

From here I tried to set the following env vars:

QT_QPA_EVDEV_KEYBOARD_PARAMETERS=/dev/input/event1,grab=1
QT_QPA_ENABLE_TERMINAL_KEYBOARD=1

but nothing happens. I tried running the application both locally or via ssh.
Do I need to set something else?