A german magazine just made a video on that topic. You can activate english subtitles.
https://www.youtube.com/watch?v=hBSEHpU-pyI
They tested a bunch of smart tvs and tv-sticks and their network activites.
They say that roku devices were the most privacy friendly tv-sticks.

And if you dont care about warranty voiding, open the tv and tape the things you dont want. Mic, cam, etc. Its probably the cheapest option

Never tried it but there is Franz and certain plugins for Bitlbee and Pidgin Messenger