FYI to all Seems like TP-Link is finally releasing (under the Tapo family of products) a 4-way compatible option. Seems to be a 3 way dimmer kit (S515D KIT), and another non-dimmer switch that may be compatible (S515). Have not yet purchased as don't seem to be shipping yet but if anyone has any luck getting these up and running, would be good to know!

 

https://community.tp-link.com/en/smart-home/forum/topic/720504

Have Kasa smart switches all over house...want to install some in 4 way configuration. Please make this happen.

  @ScottMan 

In you video, you had mentioned that if you install the smartswitch at the load side, the smart switch may lose power for a split second if one of the dumb sritched was flipped to slow.  My setup is where the line comes in, there is not a neutral wire there and i cant pull one.  However at the load side, there is a neutral wire available along with another line.  What would happen if i used another line wire to power the smart switch at the load side? Would this work and would this be an electrical hazard?