I did have Kubuntu in the first time and it did run with sddm and I was happy.
After installation of LXDE at first, synaptic did interchange sddm with an other (LightDM ?) I don´t like at all.
As I prefer LXQT, I did reactivate sddm.
But...
...I can´t access to lxqt any more

Although I can ready on all places, that SDDM is/was the standard display manager for LXQT.
a/ how to procede to the adequate setting?
Reading all that less digest stuff, I did discover that it seems to be possible to use an other Window Manager as Open Box.
b/ Which WM´ s can be used with LXQT? How to make the test/change?
An overview of the divers alternatives and profits / inconvenients?