On many Ethernet devices, you find magnetics - a transformer - as part of the physical layer.
The example above is from a TI TM4C launchpad. It looks like a solid block - like a silicon package.
I have a defect launchpad so I scavenged some parts.
To my surprise, this is how the transformer looks like from the underside:
Surprisingly old school.
Supplier's schematic: Pulse HX1198FNL