I've tried many different boards to get a solid connection through walls, floors, etc. This is the best I've found. Use them as outdoor sensors and sneak into the garage through three walls.
MikroTik S+RJ10 Ethernet Transceiver
10 Review
π‘ CM19A R.F. PC Transceiver for X10 Devices
8 Review
π Gigabit Ethernet Media Converter, Single Mode Dual SC Fiber, 1000Base-LX to 10/100/1000Base-Tx, up to 20km, 2-Pack
9 Review
TRENDnet TC-TP1 Network Signal Testing Probe with Adjustable Volume, Speaker and Compatibility for TC-NT2
8 Review
π StarTech.com NETRS2321P: 1-Port RS232 to Ethernet IP Converter, Serial over IP Device Server - Black
5 Review
π StarTech.com NETRS232 Serial to IP Ethernet Device Server - DIN Rail Mountable - Serial Device Server - Serial Over IP Device Server (Black)
4 Review
π uni USB C Hub with Ethernet Adapter, 4K HDMI, Gigabit Ethernet, and 3 USB 3.0 Ports for MacBook Pro, iPad Pro, XPS
11 Review
π USR-TCP232-410s: RS232/RS485 Serial to Ethernet Adapter/IP Device Server with DHCP/DNS Support
4 Review