Can I ask what is the problem if user finds out mautic login page?
Some suggestions that might help the underlying problem you have (the reason you want this in the first place):
- If this is because they try to login to Mautic, may I suggest you install and configure fail2ban or something similar?
- Modify web server config (apache, nginx, etc) in a way so that its possible to login to mautic only from allowed ip (yours - make sure you this config only applies to /s/login)
So far I have not done what you are asking and I do not think there is elegant solution for this on the application level.
Furthermore you should be able to make a redirect from domainname.com/mautic to domainname.com/ by adjusting web server config and only allow access to mautic login page if the user navigates directly to domainname.com/mautic/s/login.php.
One thing to test and play around with to see how it goes (obviously not in production environments) are reverse proxies.
You setup a custom page with form which you name however you want and then on web server level you forward it to /s/login endpoint which you are only allowed to access from your server´s ip (this was not tested and its only an idea, while the stuff above describe more common approaches).