3 way version of my similar 2 way case. Used to house a modified 3channel 5v opto-isolated relay board similar to: https://www.aliexpress.com/item/32753936935.html
Located in a wall behind an existing light switch or power-point either floating or screwed to a stud or frame. Existing 110/230v cables are connected to the relay output and switch the light or load. The 5v control is via the Ethernet cable / GPIO or switched by the existing light switch. No neutral required because the control power is +5v via the ethernet cable.
Solder an additional Ethernet connector with terminal block and this provides a simple way to connect various sensors or the existing switch back to a GPIO controller.
1 x RJ-45 180degree connector - https://www.aliexpress.com/item/32918645271.html
1 x RJ-45 breakout board - https://www.aliexpress.com/item/33031656602.html
1x 8way 2.54MM Pitch spring terminal block https://www.aliexpress.com/item/32797749429.html
The idea is based on a smarthome model where transformers/voltage regulators and WIFI controllers are not located in the wall at the switch. They are located centrally in a metal fireproof enclosure.
Plug the the Ethernet cable in and switch the relay from GPIO or connect the original switch and override the lights ON locally. Can also be used in combination with capacitive touch sensor mounted on the back of a blank plate or, RCWL-0516 motion detector. Example here is shown on the back of a single light switch.