After installing this package, you can change the theme in fcitx5-configtool: 1. Open "Fcitx 5 Configuration" from desktop menu. 2. Open Addon configuration tab. 3. Configure the "Classic User Interface". 4. Change the theme. To run fcitx5-configtool, you need to install fcitx5-config-qt or kde-config-fcitx5 (only for KDE users).