@thevar1able https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/

enu1u1u1 comes from the network adapter on the RPi3+ being a USB-ethernet-chip connected through an USB-hub to the host USB controller (each u1 denotes the USB-Device number on that level).

You should be able to look at the `lsusb` output and confirm that.

Also, you can select a different name with some udev rules.