As has been clarified in many posts, we are not allowed to reference an external script in the Manifest V3 Chrome extension. One suggestion is to copy the script into the extension.
I am not sure how to implement this suggestion for the Paypal script mentioned in this error:
To begin with, how do I download the script? I tried doing "Save as..." from the browser, but got "File not found". I tried wget https://www.paypal.com/sdk/js, but got the 400 response.
