What is the ruling on profiting from developing technologies such as e-wallets and cryptocurrencies, which aim to facilitate commercial exchange, knowing that these technologies may be used by banks (whether directly or indirectly) and others, and their use cannot be limited to Islamic banks only?

The basic principle concerning the development of financial software is permissibility (حل). There is no prohibition in non-Islamic banks using such software, as long as the program is not specifically designed for them. There is no harm in this, as it does not involve direct or intentional assistance in what is unlawful (حرام). However, it is not permissible for the developer to deal directly with a usurious bank, due to the cooperation in usury that this entails.