I live in a 2-story house. There is a set of staircase lights that was being controlled by two regular Leviton switches, one upstairs and one downstairs.
The downstairs gang box has only one socket for the switch, upon opening up the box I found that there are only four wires. White, Green, Black, and Red. It's missing the second black wire I usually see in other gang boxes. The WHITE wire is connected to the black screw of the Leviton switch. The red wire is connected to the gold screw above the black screw, the black wire is connected to the other gold screw, and the copper wire is connected to the green screw.
The upstairs gang box is also interesting. For the switch in question, the black screw is connected to a black black wire that's in its own sheath. The gold screw above it is connected to a black wire, which comes out from the same sheath from the red wire that's connected to the other gold screw, and the copper wire is connected to the green screw. The interesting part is that this socket's WHITE wire is twisted together with a cluster of BLACK wires which I think are the LINE wires for the other sockets.
When I was testing for line and load wires, the downstairs black screw was the LINE, but like I said the black screw is connected to the WHITE wire. I suspect the WHITE wire is carrying the LINE power from the upstairs cluster.
How should I install two smart (Brilliant) switches that have a black, red, white, and green wire and control the staircase lights?