Looking for logging into the Jira User 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 User site. After that you can login as usual with your login credentials.
https://confluence.atlassian.com/cloud/log-in-as-another-user-776994835.html
https://jira.atlassian.com/browse/JRASERVER-2134
https://community.atlassian.com/t5/Jira-questions/how-do-i-login-impersonate-as-another-user-in-Jira/qaq-p/63241
https://confluence.atlassian.com/jirakb/unable-to-login-to-jira-applications-596770904.html
https://community.atlassian.com/t5/Jira-questions/Currently-logged-in-users/qaq-p/388195
https://community.atlassian.com/t5/Jira-questions/I-need-to-login-with-username/qaq-p/373591
https://community.atlassian.com/t5/Answers-Developer-Questions/JIRA-is-it-possible-to-get-user-login-history/qaq-p/489043
https://community.atlassian.com/t5/Jira-questions/What-does-quot-Any-logged-in-user-quot-mean-in-JIRA-permission/qaq-p/682383
https://marketplace.atlassian.com/apps/1211740/user-switcher-for-jira
https://community.atlassian.com/t5/Marketplace-Apps-questions/Login-User-within-Plugin-Jira-7/qaq-p/99038
https://community.atlassian.com/t5/Jira-questions/JIRA-Login-Username-Password-Incorrect/qaq-p/4375
https://community.atlassian.com/t5/Jira-questions/Why-do-all-users-need-to-be-in-the-Jira-users-group-therefore/qaq-p/100339
https://de.atlassian.com/software/jira/pricing