darkly is necessary.

Installation via the KDE themes store:

• Navigate through System Preferences to "Global Theme."
  
• Select the "Get New Global Themes" option in the top-right corner.
  
• In the new window that appears, search for "Banff" and click "Install."
  
• Now, go back to the Global Theme section, select the newly installed theme, Banff, and ensure both checkboxes are enabled: "Appearance settings" and "Desktop and window layout."
  Click "Apply" and watch as your desktop's appearance transforms completely.
  

Installation in Console:

• Download the file from this site.
  
• Open a terminal (console) in the downloads directory.
  
• Use the following command: kpackagetool6 -i Banff.Dark.tar.xz