I have been installing Kasa smart switches in my house. The switches require load wires, neutral, and ground. This box is troubling me. (pictured) It looks like it’s wired for a 3-way but there is no other switch connected that I know of. How can I connect this to a 2-way smart switch?
Turned this from a comment into an answer ( can take a hint)...
There may have been another 3-way switch that was removed. If that's the case, then one of the travelers is probably no longer used. Disconnect them one at a time and try the switch. That will identify which traveler is still being used, which is now just a switched HOT. And that's the one you need on the load side of you smart switch.
The wire on the black screw should be the hot that is switched between travelers,
Don’t forget sometimes the 2nd switch can be in another room or even in a different place like a garage.
Make sure to label any wires that you remove because it wouldn’t be the first time someone pulled a 3 way capped the one wire that appeared to not do anything then someone flipped the other switch months later and they couldn’t figure out what was wrong.