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Sorry about that 🙃
Personally, I think that if a TV is advertised as having certain apps, there should be a legal obligation on the app providers to keep them running for (say) a minimum of five years from the date the model is superseded, or declared no longer current, i.e. the same obligation there is on the providers of the hardware components.
But the practical path when your favourite apps start to be supported no longer, is to buy a smart device and plug it in to your TV, of which the Roku Sticks and Boxes are easily the most versatile.
This means the TV can maintain, or even upgrade, its current smarts for as long as its HDMI ports stay supported.