I think that is exactly what I have my antenna feeding in to and then supply three drops. Have a tuner card and TV that are used most of the time as well as a TV that just sits there in a bedroom. Want to get a HD Homerun sometime though. I rarely use the tuner card and would enjoy having Plex just record stuff so I can watch it later if I want to.
Why buy that when you already have what you need, a TV Tuner. All that device has is a small purpose built computer running software that is available for you pc and a built in tv tuner. You can use Kodi to do everything that this device does on your computer that has a tv tuner in it and use plex to fling it to all your devices.