I seem to have found a solution. Install polkit, in my case
sudo apt install lxpolkit
And then, it may be useful to check the Default applications in Menu ->
Preferences -> Default applications for LXSession , select Core
Applications , and make sure 'Polkit Agent' is set to lxpolkit.
Is it possi
I am having similar problem in Lubuntu 18.04 LTS. I found it originally
when I run 'Software and Updates' from the menu (software-properties-
gtk) and try to check/uncheck software sources. Checking/unchecking does
not work. I can only see the error message "ERROR:root:Authentication
canceled, chan
