Adding another information:
I retested it on Debian Buster and Stretch and the same error prompt
appears when LXDE is not started from the actual screen/console but when
calling "startx" from e.g. an SSH session, which then start LXDE on the
main screen. The solution/workaround is the same.
Interestingly there is not a single lxpolkit process running then, so it
is not a conflict between multiple lxpolkit. I'm not sure whether
disabling it completely is the right thing, respectively of any negative
impact when doing so. Probably there is something missing or lxpolkit
needs to be actively configured to work fine with LXDE?
I hope this helps to track down the issue.
Best regards,
Micha
