Is it permissible to dispose of usurious gains by donating them to hospitals for the purchase of medical supplies and medicines, or by placing them in the mosque's charity box, given the inability to identify a specific poor or needy person?

There is no harm in getting rid of usurious gains by placing them in a donation box for Muslims or in the mosque's donation box to be spent on its interests. This is the more preponderant opinion. Al-Ghazali mentioned that unlawful wealth whose owner is unknown should be spent on the general interests of Muslims, such as mosques. It must be noted that it is not permissible to keep an interest-bearing account except out of necessity.