The function to invite users to your list is only activated after a registration. Please note that Firefox disallows opening links in the app by default (see Firefox Links). You can find more about the login in the section In the side menu, click on "Edit list" next under the list name. Under the item "Authorized users" click on "Add user to list". Select permissions for the user to be invited (a "User" can use the list normally, an "Admin" can additionally manage the users). Click on "Invite user" and share the text through any platform. The invited user must now click on the link and open the app. A popup opens where the synchronization must be confirmed