Ubuntu 18.04 MSI Carbon B450 Ethernet Problems

Download the Intel network adapter driver I211 from here and follow the instructions from the README file:

tar xvfz igb-5.3.5.22.tar.gz
cd igb-5.3.5.22/src
sudo apt install libelf-dev
make -j$(nproc)
sudo make install
sudo rmmod igb
sudo modprobe igb
sudo update-initramfs -u