You need to assign the module roles that the anonymous user needs to the anonymous user role.
So let’s say we have a module products and this contains an entity product with permissions to view with the role readonly, if the page that shows the products has this module role readonly as well and you want the anynous user to access the page. Make sure that the anonymous user role has the module role readonly from the products module assigned and there is a page for the anonymous user to land on when accessing the application (via the navigtion) you are good to go.