What is the ruling on depositing money in an interest-based bank due to the unavailability of Islamic banks, and does this contradict the prohibition of leasing a building to an interest-based bank?

It is not permissible to rent out a shop or a house to someone who will use it for sinful purposes, such as an interest-based bank, because it constitutes aiding in sin. Jurists have explicitly stated the invalidity of renting out property to be used for prohibited activities like usury. As for depositing money in an interest-based bank, it is forbidden, whether with or without interest, because the bank uses these funds for usury. An exception to this is a case of necessity, such as someone who fears for their money and cannot find a safe place to keep it; in such a case, it is permissible for them to deposit it in a current account without interest, because necessity is judged according to its extent.