You'll first need to access your Intelligent Wi-Fi settings by opening your Settings app, tapping on the Connections tab, then Wi-Fi, then the three dots (for expanded settings) on the top-right ...
Over on the tab with What's On Netflix, select your desired code, and place it at the end of the URL. For example, the "Fantasy Anime" subgenre code is 11146, so I altered the URL to read: https://www ...