A backend implementation for xdg-desktop-portal that is using Qt/KF5/libfm-qt.

Use LXQt filedialog in applications

- Firefox: In the address bar about:config,widget.use-xdg-desktop-portal has to be set to true.
- Thunderbird: Preferences > Configuration Editor - as above
- Other GTK applications can be started with GTK_USE_PORTAL=1 application

A general use of GTK_USE_PORTAL=1 in ~/.profile or /etc/profile can lead to issues and is not recommended.