I’d say the behavior you’re describing is perfectly normal. The regular URL that is shown in the address bar while you’re logged in to your instance can only be used, well, while you’re logged in. If you want to be able to access an album or folder without being logged in, you need to use the public share link: (the link with the “…/s/…” in the URL), otherwise you will be redirected to the login page, which is intended behavior.