Is it permissible to allocate waqf funds to support youth and sports centers that aim to protect young people from deviancy and develop society, and what is the legal evidence for that?

The jurisprudential rule is: "The condition of the endower is like the text of the Lawgiver." So, if the endower specifies a particular use for the endowment funds, it is obligatory to adhere to it while considering their intention. If the funds are endowed for charitable acts in general, then it is permissible to spend them on any aspect of goodness, including beneficial youth activities that are free from prohibitions and are governed by Islamic regulations.