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.