Affects LXQt installed as the original Desktop on Tumbleweed.
Problem does not exist on LEAP.
All instances and experimentations were in Virtualbox, but it's my impression
none of these problems can be traced to VBox.

To Reproduce:
Tumbleweed install (DVD or Net)
When screen prompts for Desktop selection, select button "Configure Online
Repositories"
After Online Repositories are configured, select "Custom"
Select LXQt Graphical Environment
Continue Installation.

The installation will continue until an error is thrown and the User is
prompted to select a Window Manager. At that point, the only WM that seems to
work is IceWM. If openbox is selected (The WM configured in LEAP 15), the
Desktop will be black, and a context sensitive menu <might> appear with a
rt-click, but only once. After that, the Desktop will respond only to a
left-click for configuring openbox, but the User will be unable to launch
anything, eg a windowed console, a menu to select an app, etc. So, the
environment is basically unusable. 

Have tried a variety of other WM as well, and have found only FVWM is usable,
every other including kdewm, twm, gdm are no improvement over the unusable
openbox. As noted, above icewm does seem to work somewhat.

Most switching between WM were done by running
update-alternatives --config default-xsession.desktop

Also tried one experiment attempting to configure a WM using the following, but
resulted in a completely unusable system, that was then paved and re-built.
LXQt Control Center > Sessions

Have done some superficial checking whether various components described by
configurations exist or are missing by comparing a non-working Tumbleweed
install with a working LEAP 15 but I haven't identified anything <missing> This
perhaps suggests a fundamental difference in the way a Window Manager is
configured and utilized between Tumbleweed and LEAP 15.

Have recommended a "Major" severity if not Critical because at least from the
perspective of installing LXQT as the <only> Desktop, the User/newbie would
have to know to select IceWM just to result in something usable, and beyond
that hardly any WM will work including what works in LeAP 15.