Gnome is typically the default for Debian, if you want that taskbar here is the doc to install KDE Plasma.

Essentially:

sudo apt remove gnome task-gnome-desktop gnome-core gdm -y

# alternatively you could also “sudo apt purge *gnome*” but there is a possibility dependencies may get caught up in this

sudo apt install kde-full kde-plasma-desktop task-kde-desktop sddm -y

# You’ll likely get prompts throughout the install

sudo apt autoclean
sudo apt autoremove -y
sudo reboot