Why does Ubuntu keep trying to connect to a WiFi network while plugged into an ethernet
Solution 1:
Well, it obviously should check for ethernet connection first, so it's a bug, and you should file a bug report against the network-manager package.
ubuntu-bug network-manager
For more info, see the bug filing howto: https://help.ubuntu.com/community/ReportingBugs
Meanwhile, disable auto-connecting to that network:
- right click the network applet in the panel
- select "Edit Connections..."
- select the Wireless tab and double click the network
- uncheck the "Connect Automatically" box