that's wrong in English, you cannot use a countable singular object without a determiner. you could also say "a newspaper".
However in Turkish we do not use plural when we talk about general stuff as in here ("çocuklar gazeteler okur" is nonsense). Plurality does not always need to match, especially when the languages are so distant. We also don't say "three newspaperS", we say "üç gazete- three newspaper" for example. There are many other instances where Turkish uses singular but English uses plural
duolingo still has shortcomings regarding grammatical explanation. İt is highly confusing where elmari is correct but gazetteler is wrong, okur and okurlar both are correct. This surely puts the morale down that we cannot learn a foreign language completely. İt always remains incomplete somewhere.