@LadyP You can use Deco E4 with ISP Modem/Router by using ethernet cable and use Deco E4 in AP Mode.

  @LadyP you can use your Deco E4 as an extender by setting it up in Access Point mode. To do this, connect one of the Deco units to your main router using an Ethernet cable, then open the Deco app and choose the Access Point mode under the settings. This will allow your Deco E4 to extend your existing Wi-Fi network instead of creating a separate one.

If you already have another Deco network running, you can also add your E4 to it as a node through the app to expand coverage more seamlessly