It appears that Duplecast IPTV does not support LG Netcast. If you have an LG TV with Netcast as its operating system, you may not be able to install the Duplecast app on that specific TV model. To use Duplecast, you would need a TV with a compatible operating system like webOS, Samsung Tizen, Android TV, or other supported platforms.
For LG TVs with Netcast, you can explore other options for accessing IPTV services, but the availability of apps and compatibility may be limited due to the older technology of the Netcast platform. You might consider upgrading to a newer LG TV with a supported operating system if you wish to use the Duplecast app or other IPTV applications that are not compatible with Netcast.
Please check the Duplecast website or contact their support for the latest information on compatible platforms and devices.