Assalamu Alaikum, it's a very urgent question: Is doing internship in a bank permissible?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

If the bank in which you are training is a usurious bank, then the basic principle is that it is not permissible to train in its usurious transactions and anything related to them. If the person is required to train in banking transactions, this can be achieved in Islamic banks.

Allah knows best.