fvwm on opensuse leap 42 freezes display manager

I am a happy fvwm user on an a somewhat old openSUSE 11.3 (I tend to upgrade only at hardware change). We recently have got some high school students for a stage, and put them on a freshly installed opensuse leap 42 workstation.
Since I wanted those working under my supervision to share my fvwm configuration (cuius regio eius religio http://www.fvwmforums.org/phpBB3/images/smilies/icon_biggrin.gif ), I installed (from yast2) the fvwm package. Most of the times it runs ok.

In a few cases I found that after logging out, the suse display manager seems frozen (the login mask does not respond). Originally I cured it with a reboot, until one day I had the same problem and a reboot did not cure it. Even when the display manager is unlocked, one enters user and password and presses login and then it freezes. If I login remotely, I see that the fvwm session has started (a ps shows the X server, an sddm process, the fvwm and the dependent processes … but nothing appears on the display) … also a “who” does not show the session.

I am not familiar with this sddm (on my older 11.3 the way the X server starts the window manager is different). The Xsession error log does not show anything significant.

I was able to cure it after a reboot logging in under KDE then logging out. After that the fvwm session started normally. Any clue ?

I haven’t run into that problem. I mostly use KDE, but I do occasionally login to “fvwm”.

You did not explicitly say, but it looks as if “sddm” is managing your login. May I suggest that you try switching to “lightdm” (you may need to install it first).

Actually, with “sddm” I occasionally ran into a problem where I would login to KDE and nothing seemed to happen. But if I used “CTRL-ALT-F1” (switch to a virtual console) and then “CTRL-ALT-F7” (switch back to the GUI), I would find that I was properly logged in.