Now you’re wondering about opto-isolation for Ethernet. Yes, there are Ethernet surge protectors. Just be careful if you are using this in conjunction with PoE. And of course there are other methods like using a UPS at the switches to protect from surges.
20180824/DuckDuckGo opto-isolated ethernet adapter
20180824/https://www.serialcomm.com/serial_rs232_converters/opto_isolated_and_surge_suppressors/ethernet_surge_suppressor/ethernet_surge_suppressor.product_general_info.aspx