Is donating to build mosques in Tunisia, where funds are collected and the donor is given a receipt from a usurious bank, considered permissible and counted as an ongoing charity, knowing that the funds will be deposited in usurious banks?

It is not permissible to deal with usurious banks, as they support usurious transactions, except in cases of necessity and need, such as the absence of Islamic banks or fear for one's money from theft. If there is a need to deposit money in usurious banks to complete the construction of a mosque, there is no objection, and the donor will be rewarded.