This looks like the problem I have in Lubuntu 18.04 (but only in systems upgraded from 16.04 - new installs seem fine).
But I can't find the magic "Policykit Authentication Agent" tickbox in Lubuntu: where is it hiding? -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/976638 Title: pkexec does not find any authentication agent To manage notifications about this bug go to: https://bugs.launchpad.net/policykit-1/+bug/976638/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs