So what kind of fix do we need?
Outside of that was found in tdebase, XDG_SESSION_COOKIE is used
in kpowersave
and tdepowersave (will be fixed after commit patch from bug 1597).
This is
good news - on the ConsoleKit no more dependent - only TDM. In
other words,
it should be enough to add support for SystemD session into TDM. I
will try
to assess how difficult this task is...