Is it permissible to guide a person to a university or school that contains some objectionable practices (munkarat), while warning him to be cautious, especially if these objectionable practices are widespread and this institution is considered among the least harmful, and does the ruling differ if the person is religious and is thought to avoid forbidden things?

The ruling on guiding someone to a university or school is a branch of the ruling on enrolling in it. If enrollment is permissible, then guiding to it is permissible. If enrollment is forbidden, then guiding to it is forbidden. It is permissible to study in the presence of some objectionable things if one is able to preserve their religion and is safe from temptation for themselves. This varies depending on individuals, circumstances, and places. A Muslim should strive to advise themselves and those around them, and endeavor to minimize evil and corruption to the best of their ability.