I am on Ubuntu 20.04 Mate Desktop. If I use nm-applet via mate-indicator-applet-complete it works well. I want to use only notification area applet instead of mate-indicator-applet-complete but if I use it as a notification area (systray) applet by adding it to startup applications list with dbus-launch nm-applet --indicator it won't prompt password dialog anymore.
I tried the following suggestion https://askubuntu.com/questions/230825/how-can-non-admin-users-connect-to-wi-fi-networks
I also tried allowing policies in
/etc/dbus-1/system.d/NetworkManager.conf
and
/etc/dbus-1/system.d/nm-applet.conf,
without success.
Running dbus-launch nm-applet --indicator as root works.