Looking for logging into the Joomla Code site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Joomla Code site. After that you can login as usual with your login credentials.
https://docs.joomla.org/API15:JApplication/login
https://docs.joomla.org/Customising_the_Login_Form_module
https://forum.joomla.org/viewtopic.php?t=872155
https://stackoverflow.com/questions/2075335/how-to-log-into-joomla-through-an-external-script
https://joomla.stackexchange.com/questions/22029/how-to-code-login-to-backend-in-joomla
https://network.convergenceservices.in/forum/40-joomla-tricks/1636-one-line-code-to-authenticate-and-login-a-user-in-joomla.html
https://github.com/chdemko/joomla-external-login
https://www.joomlart.com/documentation/joomla-module/ja-login-module
https://www.youjoomla.com/joomla-extensions/yj-pop-login-free-joomla-login-module.html
https://www.joomlashack.com/blog/joomla-how-to/how-to-simplify-default-registration-form-in-joomla-3/
https://www.youtube.com/watch?v=AuEq-cE2ehI
https://www.joomshaper.com/blog/joomla-admin-login-pages-change-like-a-pro
https://www.web357.com/joomla-extensions/login-as-user