Redirect Guests to Login

In Settings > General > Redirect Guests to Login enabled, it redirects to the main WP login page. This is not ideal for other integrations such as Ultimate Member that some sites use to handle registration/login forms.

If it is not easy to work with all of the possible login/registration integrations, then maybe you can have a custom login redirect URL field for that.

Also, when Redirect Guests to Login is disabled, there is a login form on the messages page, but there is no registration button for users who are not signed up yet.