What is the ruling on taking an interest-based loan in the form of Murabaha to purchase equipment for a consulting firm, knowing that the bank is a branch of a French bank?

If the transaction is based on the bank paying part of the price on your behalf without first acquiring ownership of the devices, then this is a prohibited usurious loan (riba), because the bank pays the amount and then collects it from you with usurious interest. As for the legitimate method, it is the true Murabaha contract, where the bank owns the commodity before selling it to the customer. The customer can pay a down payment and pay the rest in installments. It is not permissible to deal with usurious banks when Islamic banks are available. If they are not available, then there is no harm in dealing with them in what is permissible by Sharia.