Learn Spanish (Latin America): La trivia no es más que un juego.

It acts as a restrictive negation meaning 'nothing more than,' 'nothing but,' or simply 'just.' Here, no es más que un juego emphasizes that trivia is only a game and shouldn't be taken too seriously. It works very similarly to solamente or solo.

Since this lesson also covers 'sino', could I say 'La trivia no es sino un juego'?

Yes! No... sino can also be used for restrictive negation meaning 'nothing but' or 'only.' Saying La trivia no es sino un juego means exactly the same thing, though it sounds slightly more literary or formal than no es más que.

Could I add 'nada' and say 'no es nada más que un juego'?

Yes, you can say no es nada más que un juego (it is nothing more than a game). Adding nada makes the statement slightly more emphatic, but no es más que is already a complete and natural way to express the exact same restrictive idea.

In English, 'trivia' comes from a plural Latin word. Is it always a singular noun in Spanish?

Yes. Spanish adopted the English concept of 'trivia' (referring to quizzes or random facts) as a singular feminine noun, la trivia. You don't treat it as a plural collection of facts, which is why we use the singular verb es.