@bad_aptitude - one could co-install LXQt without problems but i would like to suggest a lxqt installation in a own partition. Maybe i'm a little bit picky if it comes to installations - i may have valid reaseons, depending on the point of view:
* Debian LXQt comes with only the needed tier 1 KF5 dependencies - the same as KDE use - so no problem
* Debian LXQt has xfwm4 asl WM - if one prefer kwin, i see no problems - the only reason for not include kwin-* right now is that LXQt has no tools for kwin-configuration, so one has to use the KDE ones - beside that i see no problems, kwin is a fine and able WM.
* One has to check twice which daemons come with kwin/KDE - it might be that there are/could be conflicting packages - not from packaging, but in functionality. That might hurt lxqt-qtplugin basicly.
* both kde and lxqt use sddm - so no problem
At least its a matter of taste, it should run just fine.