From what I’ve been reading, only Stripe is supported, which is not available in some countries (such as Chile). I would understand that if other platforms need to be implemented (such as Paypal) it would require additional development. Is this really the case?
Yes, it requires additional development to include other payment methods. A key feature tied to Stripe in Ghost is to create membership tiers, if Stripe is not connected in Ghost, then you can’t set up multiple tiers for your members, and you can only classify them as paid or free users.
Here is a doc about incorporating Paypal into Ghost: