Not exactly rocket science but since it took me a while to find out I’ll keep this here for future reference: to get rid of NetworkManager authorization prompts in openSUSE Leap 15.0 and similar distros, create /etc/polkit-1/rules.d/80-networkmanager-allow-users-group.rules:
polkit.addRule(function(action, subject) { if (/^org\.freedesktop\.NetworkManager\./.test(action.id) && subject.local && subject.active && subject.isInGroup("users")) { return polkit.Result.YES; } });