You put a trusted intermediary (JP Post) that knows the address in the middle, and provide the seller with an identifier that the intermediary can associate with your physical address.

That’s already how it works if you buy something trough the online marketplaces here - Mercari et. al.

Mercari knows addresses of all counterparties, but the label that the seller puts on the package doesn’t have the destination address, and the label the package has when it reaches your door doesn’t have the seller’s address either.