Yesterday I upgraded from Leap 15.5 to 15.6 using zypper dup as explained on a
opensuse site. The 15.5 had been very stable. Since the upgrade the X11 session
 hung twice. The first was yesterday when a youtube video was playing in Chrome
and the sound just continued forever as if nothing happened while the screen
was totally frozen. Ctrl+Backspace and Ctrl+Alt+F1 didn't work and a hard reset
was the only way out. Today the screen again froze totally, except for the
mouse. The mouse pointer was movable over the screen and this time
Ctrl+Backspace did work and gave me the GDM login screen. Couldn't find
anything in dmesg or in Xorg.0.log. Needless to say, this is very disturbing to
me.
This is a previous Xorg bug from me for details:
https://bugzilla.opensuse.org/show_bug.cgi?id=1214448.

There is now another problem. I run icewm as a window manager and GNOME
applications like gnome-calculator and evince take 40 seconds to appear. strace
shows they block on a futex a couple of times, but unclear what they are
waiting for. This is very annoying too. If I want to read PDFs it now takes
ages.

There is also this in my environment which I don't know how to influence as
there seems no documentation about, hence I can't figure out how to tweak it:
GTK_IM_MODULE=cedilla
GTK_MODULES=canberra-gtk-module:canberra-gtk-module
Can I unset this, or are these needed for the GNOME applications, or what can I
do with them?

Thanks for your time and attention.