As been suggested, IF you DON'T actually need Ethernet functionality then -
RS232, up to 38K4 Baud will travel 100Meters
Use a cheap RS422/485 chip and that extends to 1-2 KM, up to 76K8
Use a cheap mutimode fiber, TTL levels, ST or SC connections and go several KMs at 115KB+,
I've made 100s of all these and can post ccts if you need.
You can also go "radio", like the garage door kits, ~2400B, or 900MHz = 76K8 to 20KM.
Lots of options