When you are opening /install or public/install you are getting 404 page instead of installation
[https://yourdomain.com/public/install or https://yourdomain.com/install]
But when you try opening using index.php in URL https://yourdomain.com/public/index.php/install You get the installer
You are not able to access the installer at /install because the mod_rewrite is not enabled on your server.
Once mod_rewrite is enabled you can access directly https://yourdomain.com/public/install or https://yourdomain.com/install