ArcGIS Enterprise Team,
When creating an enterprise account with a SAML login, the organization's enterprise ID is not added to the end.
Example: in 10.6.1 the result would be firstname.lastname@example.org_trpd
In 10.7.1 and now 10.8 the result is only email@example.com.
This has been formally logged as a bug #BUG-000124838 in Esri Case #02386306 back at 10.7.1
and the only provided workaround is to use code-
"Add users using either the command line utility or by modifying the sample Python script. Set the IDP Username value to their SAML account name and the login value to their SAML account name plus the defaultIDPUsernameSuffix."
Esri team, this is not a sufficient workaround, please look into this issue.