Bought a 6 year old high end custom home with a 4-way switch that I wanted to convert to a smart switch. Had a handyman with an electrical background successfully install several Kasa smart switches...

@septer012 I had an electrician install two Kasa 3-way switches at each end of my 4-way set up, leaving the middle switch a dumb switch (the one with 4 wires). It never did work, even using the Kasa...