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. What I do if that happens is rename the new ethernet connection to match its physical device name. Then I delete any new bridge and the old devices. Finally, I rebuild it all as indicated below. I'm sure there's an easier way to do this (starting with disabling "predictable device naming"). Maybe someone will tell us what it is in the comments.
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 "enp2s
