Looking for logging into the Screen For External Domain 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 Screen For External Domain site. After that you can login as usual with your login credentials.
https://social.technet.microsoft.com/Forums/en-US/67c9d0e4-1a30-475a-a2be-683718d721ae/multiple-login-prompts-and-blank-screen-for-external-user?forum=sharepointgeneralprevious
https://portal.smartertools.com/community/a86402/unique-domain-login-screens.aspx
https://community.spiceworks.com/topic/491925-first-login-of-domain-user-outside-company-network
https://help.salesforce.com/apex/HTViewHelpDoc?id=domain_name_login_branding.htm
https://fastmail.blog/2013/06/06/custom-login-screens-for-familybusiness-accounts/
https://salesforce.stackexchange.com/questions/6012/custom-sites-domain-name-redirecting-to-salesforce-login-screen
https://manuals.gfi.com/en/kerio/connect/content/email-clients/webmail/how-do-i-create-a-custom-or-external-login-interface-for-webmail-322.html
https://support.icewarp.com/hc/en-us/articles/115000745368-WebClient-Login-Screen-Customization
https://community.logmein.com/t5/LogMeIn-Pro-Discussions/Logging-in-with-Windows-7-Pro-and-a-domain/td-p/35357
https://moodle.org/mod/forum/discuss.php?d=5069
https://confluence.atlassian.com/crowdkb/redirected-to-the-login-screen-with-no-errors-when-attempting-to-log-in-to-any-atlassian-applications-376834420.html
https://www.youtube.com/watch?v=XGO9pxElZV8
https://auth0.com/blog/using-centralized-login-to-add-authentication-to-your-ios-apps/