Scenario:

I have a public website e.g. www.mywebsite.com

I have a beta website, not yet production ready e.g. private.mywebsite.com

This would allow us the ability to have our website live in a version that isn't quite production ready, allowing us to share it with other users without needing to set up local dev environments, or requiring any additional dev work on our apps to require a password for access

The easiest way I believe this can be achieved is by utilising passwords defined in the .htaccess file

Example: https://www.lcn.com/support/articles/how-to-password-protect-a-folder-on-your-website-with-htaccess/