Ubuntu wired unmanaged

First, you need 'network-manager'

sudo apt install network-manager

Second, edit the file /etc/NetworkManager/NetworkManager.conf
like below picture, change a 'managed=false' to 'managed=true'

sudo service network-manager restart

if it doesn't work, follow below command

Edit file /usr/lib/NetworkManager/conf.d/10-globally-managed-devices.conf

From

[keyfile]
unmanaged-devices=*,except:type:wifi,except:type:wwan

To

[keyfile]
unmanaged-devices=*,except:type:ethernet,except:type:wifi,except:type:wwan

sudo service network-manager restart

It may work for all.