We have a smart TV on the way. We do not plan to run the setup, it won't have Internet access. We plan to do what we've done for over a decade now, connect our Kubuntu laptop in the entertainment center to it and select it as the default input device. And occasionally watch OTA TV shows. So we will use it as ... a monitor and plain TV, that happens to have far better video and sound quality than our old TV.

that's the same conclusion I came to and the device I am developing is basically a Raspberry Pi with my own modified OS that has a casting canvas and it can show all kinds of content.

No third-party installs, ads and spywares!