For example, I have only one shipping method (Flat Rate) configured that is available for the US country only. When another country selected and the "No shipping method available" message received I still want to proceed with payment as I will send custom shipping offer to the client via E-Mail. By default, if no shipping method selected I could not finish the checkout.
How is it possible to proceed with payment in checkout without shipping method for address entered available?
A virtual product is not an option.