For giggles a few years ago I made myself one of these hubs:
https://www.eeweb.com/building-a-passive-ethernet-hub/
On Amazon you'll find "ethernet splitters". They might be what you're looking for, (I treat them as a last resort thing if you can't lay multiple long cables or a local switch):
RJ45 \ / RJ45 splitter ------long cable ------- splitter RJ45 / \ RJ45
For giggles a few years ago I made myself one of these hubs:
https://www.eeweb.com/building-a-passive-ethernet-hub/
On Amazon you'll find "ethernet splitters". They might be what you're looking for, (I treat them as a last resort thing if you can't lay multiple long cables or a local switch):