What would be the best way to have close to 30 Ethernet connected IoT devices spread over a large area?

I cannot use any type of wireless technology for this project due to regulations. I'm thinking I'll have a Switch at the main data entry point and that will split off into the IoT devices. The problem is that many of them will be greater than 100m away from the Switch and there are no access points that far away. What would be an affordable solution to this? Some kind of ring structure where they are all connected with some kind of signal booster at certain points?