I carried out further tests, until I replicated the problem on a virtual
machine.
Then I compared the plasma configuration subdir with a functioning
version (obtained experimentally, resetting the arrangement of the
desktop and windows, from default breeze theme).
The difference that determines the problem is in the
"~/.config/plasma-org.kde.plasma.desktop-appletsrc", section
"[Screenmapping]".
I noticed that "itemsondisabledscreens" and "screenmapping" items have
an excessive line length.
LENGTH LINE
BYTES FIRST 200 chars
82 --- ok-plasma-org.kde.plasma.desktop-appletsrc 2023-07-03
13:26:44.894
83 +++ bad-plasma-org.kde.plasma.desktop-appletsrc 2023-07-03
12:35:57.69
16 [ScreenMapping]
24 -itemsOnDisabledScreens=
392
-screenMapping=desktop:/4.png,0,71c04f84-b363-4dca-a9a8-671fbb033f34,d...
14110
+itemsOnDisabledScreens=2,19c9821c-6bd3-4d27-b17a-1e325203a1fc,1,deskt...
3994359
+screenMapping=desktop:/safekernel-bk110323.01-rel6.1.18/build/include...
This was also noted from the file size:
Bad:
-rw------- 1 root root 37K Jul 3 13:43
~/.config/plasma-org.kde.plasma.desktop-appletsrc
Good:
-rw------- 1 root root 12549 3 lug 13.47
~/.config/plasma-org.kde.plasma.desktop-appletsrc
If I remove the entire section, everything works well.
I don't know why, but these lines have elongated dramatically. Perhaps
the processes that manage them do not control the maximum length of the
lines ...
With the previous version of Libc this problem had never occurred, even
in the presence of these lines; while with the new version he came out.
However, now the problem seems to have solved.
