Ubuntu Wiki

There is a bug with plasma-widget-networkmanagement, that prevents from connecting to a mobile broadband connection.

https://bugs.kde.org/show_bug.cgi?id=191658 https://bugs.edge.launchpad.net/ubuntu/+source/plasma-widget-networkmanagement/+bug/334122

A workaround for this problem is to edit

nano ~/.kde/share/apps/networkmanagement/<connection>

and replace MTU=0 and MRU=0 with MTU=1440 and MRU=1440. After restarting services and probably the whole system the connection should work.

Be careful with this kind of connections, making a mistake here, might be very expensive.