История изменений

А не, судя по ArchWiki таки Openbox: https://wiki.archlinux.org/index.php/LXQt#Use_a_different_window_manager

UPD А с другой стороны

LXQt does not provide its own window manager but any arbitrary window manager can be used, most notably Openbox, KWin, the window manager of KDE, and Xfwm4, the window manager of Xfce.

https://github.com/lxqt/lxqt/wiki/ConfigWindowManagers

А не, судя по ArchWiki таки Openbox: https://wiki.archlinux.org/index.php/LXQt#Use_a_different_window_manager