Praise be to Allah.
No zakaah is due on wealth that has been given as a waqf for the common good, such as to help the poor, or maintain the mosques, or those who need to get married, because it is does not have a specific owner. This has been explained previously in the answer to question no. 130229 .
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:
With regard to money that her family donates for the purpose of marriage, or giving charity, or giving to support jihad and the like, no zakaah is due on it… because it is not the property of anyone. When wealth is given as a waqf to be spent on common interests, it does not belong to those to whom it is entrusted, therefore it is not the property of anyone. End quote.
Majmoo‘ Fataawa Ibn ‘Uthaymeen (18/194).
And Allah knows best.