We have merged new Ethernet State Tracker into master branch from the eth branch. You can get it with the normal repo sync. It is still in an early stage, Chih-wei has pointed out that we missed some features like status icon and notifications for the connection up and down. we will continue to work on it.
For now, the ethernet is enabled by default. If you don't want to use it, you will have to manually disable it from the setting.
Please report the issues you found in Android-x86 discussion group.