please help me correct this sentence.

People have mixed views on what is  the main function is of universities.  (Avoid splitting the infinitive; otherwise, the sentence structure becomes awkward).

Is - third person, singular of the verb "to be"

People have mixed views on what is the main function of universities.

People have mixed views on what the main function of universities is.  (although die-hard grammar police would assert "no" you cannot end this sentence with "is",  such stuffy old rules are no longer the rules).  I grew up with the old rules that argue, for example, that you cannot end with a preposition and I still avoid doing that in a sentence.  But again, it's no longer necessary.