You can accept donations with only PayPal. To accept donations with PayPal, add your PayPal email in your Donorbox account settings

However, we highly recommend Stripe because it is a faster checkout process for donors who don't have PayPal account. With PayPal the donor will be redirecting to Stripe allows the donor to enter her card number directly in your donation forms. It's most optimal to use both Stripe and PayPal.