To determine the default file manager run the following command.
xdg-mime query default inode/directory
codium.desktop
In order to change the default manager you have to know what the desktop entry file name is called. Desktop entry files are typically stored at a couple location on a Linux system, “~/.local/share/applications/” for user-specific applications, and “/usr/share/applications/” or “/usr/local/share/applications/” for applications installed system-wide. Try locating the application name by browsing each of those directories listed or searching by using the find
command.
Here is an example of a search for GNOME Files (nautilus) within the directory “/usr/share/applications/”.
find /usr/share/applications/ -iname "*pcmanfm*"
/usr/share/applications/pcmanfm.desktop
/usr/share/applications/pcmanfm-desktop-pref.desktop
The below command example will set GNOME Files (nautilus) as the default file manager.
xdg-mime default pcmanfm.desktop inode/directory
To verify if the change worked, you can run the following command.
xdg-mime query default inode/directory
pcmanfm.desktop