Replace light switch with smart switch, existing wiring used to be three way

There is a light switch that controls some recessed lighting that I want to replace with a smart switch https://www.belkin.com/us/p/P-WLS040. The old light switch is a three way switch that is wired as single pole.

• There are two red wires for line and load on the old light switch.
• There is two black wires wire nutted together in the back of the receptacle.
• There is one white wire wire nutted by itself in the back of the receptacle.
• There is one white wire that is not stripped, just sitting by itself in the back of the receptacle.
• There are two ground wires twisted up together in the back of the receptacle.

Picture https://imgur.com/a/kBPylL0

I’ve tried tying the smart switch line with what I think is line, smart switch load with what I think is load, the smart switch neutral with the white wire nutted wire, and left smart switch ground wire nutted alone. When I flipped the circuit breaker back on, nothing happened. The smart switch didn’t "turn on", and pressing the button on the switch didn’t turn any lights on/off.

Do I need to strip the other white wire and tie all the white wires together?

https://imgur.com/a/7FKT491 Here is the other switches controlled by this circuit breaker. They are two single pole, the right one controls a hallway light and the left one controls porch lights.