The login page is an automatic page, common to both catalog and project sites, which looks like this by default:
The text on the left of the login form can be customized with content.
To do this, in the catalog site, create an "Article" content type, labeled Special contents > Authentication page content.
Please note that this content must be public to be accessible in anonymous mode.
Don't forget to add a link to the registration page to create an account.
Example of customization: