- Activate PayPal in the shop channel (with a valid sandbox configuration).
- Create a product a simple product.
- Enable Subscriptions on that product.
- Into the product configuration disable the toggle "Shippable".
- Add product to the cart.
- Proceed to checkout.
Complete the checkout without problems.
Can't complete the checkout because of the error "Please select a valid payment method." (No log errors or console).
If you edit the "default" SKU and add a price you can complete the checkout without problems.