Had to do this for some advanced networking with KVM, and couldn't figure out how to do it using the Nework Manager gui. Did find an article later that showed how to do it with nmtui, but it's so much easier to record what you did when using the cli.
IMPORTANT SAFETY TIP: Adding or removing PCI devices, like discrete graphics cards, almost always results in changing the "predictable device name" of your physical network card. This can be prevented by the addition of a simple udev rule (see below).
In the examples below "eth0" is the name of my physical interface. By default on Ubuntu and most distributions that will almost certainly be different, for example: "eno1", "ens1", or "enp2s0".
To see what everything looks like before starting: