What is the Shariah ruling on investing endowment funds in investment portfolios?

The question contained two matters: First, the endowment of money, which has been discussed previously. Second, investing endowment funds in investment portfolios. This depends on the nature of the investment in these portfolios: Is it based on usurious interest, Islamic Mudarabah, or something else? Judging a thing is a branch of conceiving it; therefore, the nature of the investment must be clarified to answer clearly.