Safari Web Extension allow external connection from any website

Hey! We are developing a Safari Web Extension which requires the background script for localhost Web Socket communication (it doesn't work if we try to connect from the injected content script), everything works fine but we need it to be accessible from any URL since we have a SDK that is distributed to the customers and the domain name depends on each of them, is there a way to do this? Or is there any workaround to not have to use browser.runtime.connect or browser.runtime.sendMessage for communication between the injected content script and the background script? We have tried to use <all_urls> but that's not allowed for externally_connectable. Thanks!