Is it permissible to use the "Buy Now Pay Later" service via PayPal in a foreign country where most transactions involve interest (ribā), knowing that payments are automatically deducted in installments from the bank? And is what I saw regarding a fatwa permitting the purchase of a car with interest due to necessity correct?

If the reality of the transaction is that the bank or entity will only take from you the actual value of the purchases without any increase in return for the deferment, then there is no usury in that. And if that entity takes a commission from the seller, there is no harm, as long as the merchant sells the goods for the same price as an immediate sale. As for purchasing a car with a usurious transaction, it is not permissible except in cases of necessity.