Yes, the iotty Smart Switch cannot be used with a traditional switch in a multi-way setup. However, you can link multiple iotty switches together (through WiFi) so they act as a multi-way switch. This is done through an extra wiring connection (no new wires needed) and configuration settings in the app.
Please visit our 3-way Help Article here.
Please visit our 4-way Help Article here.
Please note that the instructions illustrate the most common traditional three-way setup, since there are many ways to wire a multiway setup, we recommend you have a certified electrician determine how your particular setup is wired and have them make any necessary installation and adjustments to achieve the iotty multiway setup shown. While the instructions show two U1s, the concept is the same for all models.