Looking for logging into the Joomla Custom Admin 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 Custom Admin site. After that you can login as usual with your login credentials.
https://www.joomshaper.com/blog/joomla-admin-login-pages-change-like-a-pro
https://extensions.joomla.org/extension/change-admin-ui/
https://extensions.joomla.org/category/administration/admin-styling/
https://www.joomlashack.com/blog/joomla/custom-template-backend/
https://www.joomlashack.com/blog/tutorials/new-admin-menus/
https://www.joomlashack.com/blog/joomla/custom-module-backend/
https://www.joomlabeginner.com/blog/tutorials/104-how-to-customize-the-joomla-administrator-menu
https://forum.joomla.de/thread/6042-administrator-login-kann-mich-nicht-einloggen/
https://stackoverflow.com/questions/18768557/joomla-change-administrator-start-page
https://www.joomlashine.com/blog/4-steps-to-make-an-effective-joomla-admin-area-for-client.html
https://www.joomlart.com/joomla/templates/ja-admin
https://www.siteground.com/tutorials/joomla/how-to-login/
https://joomla.stackexchange.com/questions/16545/admin-login-with-url