Some technical journals have warned against buying smart TVs (per se) because of the problems caused when manufacturers cease supporting the apps on them (or when the service providers associated with those apps no longer stream content in a form which can be used by the apps).
Manufacturers have to pay licensing fees to have certain apps incorporated into their TV sets. If they cease paying those fees the apps will no longer work. Alternatively they might put on app onto a TV for, say, Youtube but, at a later date, Google ceases streaming videos in a format compatible with such apps.
So it's not uncommon for the apps on smart TVs to stop working after only two or three years. e.g.:
http://jillcataldo.com/youtube_being_discontinued_sony_televisions/
See here for further information about the problem:
https://blogs.which.co.uk/technology/tvs/when-smart-tv-app-support-vanishes-what-next/
The solution is to buy a 'non-smart' TV and then to upgrade it with an add-on device (such as a NOW TV box or an Amazon Fire TV stick). The manufacturers of such devices need to ensure that they keep them working fully (otherwise they'd lose new sales) and you can always switch to an alternative device (at very little cost) anyway.
My own choice is to use the (excellent) NOW TV box:
http://www.nowtv.com/box