It is true that you can use scenes to replace 3-way and 4-way switches. Essentially have one switch that actually controls the light and all other switches in the scenes control themselves and the master switch such that if any switch is on, all are on and if any switch is off, all are off.
The downside to this approach is that it does not work if the Internet or wifi network is down. When that happens only the one actual switch will control the light by manual action.
I made a suggestion to another manufacturer a while back that they produce a 3-way switch and incorporate a current sensor. This could be used to replace only one switch in a multiple switch situation and leave the other manual toggle switches in place. The state of the light would be known by the app software based on the current load. If the light is burning if would be drawing current. Toggling the wifi controlled 3-way switch would turn it on and off as would the other manual switches in the circuit. All the while the app software would still be able to determine the state of the light bulb.
I have one light on stairs, but first switch is upstairs and second switch is downstairs. So when I go from downstairs, I turn on light in first switch and at upstairs I turn off with second switch. It is possible? Can I use two Sonoff Touch switches?
Why not connect all N of the switches parallelly to the light and still use scenes? This way, all of the switches would work if there is no WiFi...