Do I need WiFi for my sensors to work?

No, your gateway will work with Ethernet or Cellular, depending on which unit you purchased.  Using Ethernet instead of Wi-Fi can have several benefits, including more stable and reliable communication, as well as improved security. Ethernet connections are less susceptible to interference from other devices and offer faster and more consistent data transfer rates than Wi-Fi connections, which can be particularly important for industrial or commercial applications where data reliability is critical.