My understanding is that no one used hubs anymore, so your collision domain goes from a number of machines on a hub to a dedicated channel between the switch and the machine. There obviously won’t be collisions if you’re the only one talking and you’re able to do full duplex communications without issue.

> Ethernet has had the concept of full duplex for several decades and I have no idea what you mean by: "hybrid on each end allows the use of the same channel at the same time."

Gigabit (and faster) is able to do full duplex without needing separate wires in each direction. That's the distinction they're making.

> The physical electrical connections between a series of ethernet network ports (switch or end point - it doesn't matter) are mediated by CSMA.

Not in a modern network, where there's no such thing as a wired collision.

> Take a single switch with n ports on it, where n>2. How do you mediate ethernet traffic without CSMA - its how the actual electrical signals are mediated?

Switches are not hubs. Switches have a separate receiver for each port, and each receiver is attached to one sender.

A hybrid is a type of RF transformer - https://en.wikipedia.org/wiki/Hybrid_transformer

CSMA is last used with 10Mbit ethernet, so that’s why radios are only relevant.

Right but the switch has internal buffers and ability to queue those packets or apply backpressure. Resolving at that level is a very different matter from an electrical collision at L1.