Is it true that some Samsung TVs do not fully support the MLB app, and the Pluto TV app? 

I have model  UN50CU8000BXZA

MLB has told me this model is not on their list of supported devices. I wish Samsung had told me!

MLB and Pluto make up the majority of my streaming.

If I'd known I'd have trouble with those apps  (and I do have LOTS of trouble) I never would have bought this TV.