Dolphin file manager on Ubuntu 22.04

To make it the default system file manager:

Check the current default for opening directories:

xdg-mime query default inode/directory

To set Dolphin as default:

xdg-mime default org.kde.dolphin.desktop inode/directory

Run on the terminal as regular user. If you want to set the default to another file manager, install the file manager, and find the correct .desktop file by searching in /usr/share/applications/ on the command-line.

To make it open in dark mode:

These styles are available after installing the packages:

sudo apt install qt5-style-kvantum qt5-style-kvantum-themes

Then, you need to tell to your system to use kvantum style for QT5 apps. This is performed by setting the QT_STYLE_OVERRIDE variable in your .profile file.

You have two alternative ways.

Alternative 1

• run echo "export QT_STYLE_OVERRIDE=kvantum" >> $HOME/.profile

Alternative 2:

• open the file with gedit $HOME/.profile
• add the line (if not present) export QT_STYLE_OVERRIDE=kvantum
• save the file.

After changing the .profile file, you have to logout from your account and login, then it will be sourced once automatically.

Now, open the Kvantum Manager app from the app-grid menu:

• Click on the submenu “Change/Delete Theme”
• Select the theme you want from “Select Menu”.
• Click “Use this theme” button.