There is no real one way to do this. But i did the following:
First I configured a ‘lamp’ to aways turn on in NHC2.
The two conditionals: if virtuals output is true, turn on the light, if is false… turn on the light.
Now the light is “always on”.
In HA we “see” the “Basic Action” between the Virtual Output and the switch.
Using some config, (a group, automation, and hiding some entities,…) I made the IKEA Light(s) (through the hub they sell) follow the state of that switch.
If you use switches without LED, i would do it a bit different, use the button like a toggle signal to HA.
In theory you can link anything together. In our bathroom, we have a dumb LED bulb, controlled by NHC2. But we have a IKEA Tradfri Control outlet (203.644.76) that cuts power to the electric heater when the light is off.