So I think @jonl was suggesting the following:
Set up a server action (API) folder called paddle and add an action file to test with:
accessible at (this is what you would give Paddle as the webhook address - obviously use your domain)
You can use this API file, like you would receiving form data from your own site, accessing the $_POST variables. You will need to know the data structure that Paddle send but you can access items really easily
e.g. if they send in item called ‘transaction_id’ you would access it as $_POST.transaction_id in DB insert/update queries or other server action steps. If the item has a space in the name, just use square bracket referencing instead i.e. if the transaction ID data item was called ‘transaction id’ you would use $_POST[‘transaction id’]
I hope this helps