[em3rgent0rdr]

I was also going to suggest that... But I imagine that the Ethernet port or antennae wire (and necessary battery to power antennae) would dwarf the size of that MCU. But thinking again, I suppose if the rules permit the MCU to be directly wired to the Ethernet cable, then could bitbang an early Ethernet standard with this MCU's pins...

[st_goliath]

If you're going to use an Ethernet jack anyway, you might as well use one that has an ARM SoC already built in and runs Linux:

https://www.digikey.at/en/product-highlight/d/digi-intl/digi...

[jagged-chisel]

“Obsolete and no longer manufactured.” :-(

[femto]

I'd do a serial connection using the UART. Serial is a perfectly valid transport.