Looking for logging into the Jira 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 Jira Admin site. After that you can login as usual with your login credentials.
https://community.atlassian.com/t5/Jira-questions/How-do-I-access-the-system-administrator-account/qaq-p/288982
https://community.atlassian.com/t5/Jira-questions/Unable-to-login-on-JIRA-Admin/qaq-p/765315
https://community.atlassian.com/t5/Jira-Software-questions/How-do-I-access-the-Jira-administration-console/qaq-p/824434
https://id.atlassian.com/
https://community.atlassian.com/t5/Jira-questions/How-to-disable-Jira-admin-login-verification-prompt/qaq-p/388126
https://community.atlassian.com/t5/Jira-Core-questions/admin-admin-can-t-login/qaq-p/365553
https://community.atlassian.com/t5/Jira-questions/Default-Username-and-password/qaq-p/460997
https://community.atlassian.com/t5/Jira-questions/How-to-reset-admin-password-in-JIRA/qaq-p/170533
https://www.syracom.de/fileadmin/user_upload/Images_neu/Zum_Thema/Downloads/ATLAS-Administrator_sGuideSecureLoginforJIRA-050916-0924-24.pdf
https://www.miniorange.com/atlassian-jira-server-single-sign-on-(sso)
https://adlm.nielsen.com/jira/login.jsp
https://help.smartsheet.com/articles/2476126-jira-connector-admin-setup-cloud-self-hosted-server
https://resolution.atlassian.net/wiki/spaces/SSSO/pages/84312072