When we import guest users into EIC via the Azure AD connector they are unable to login. We are mapping the UPN > Username. The Microsoft generated UPN for guest users contains the '#' character and we believe this is causing the issue as when these character are manually removed from the username they are able to login. I'm assuming special characters are not allowed in the username value and if so how should we be escaping these characters?
We do not recommend having a '#' character in the username as it may cause several issues either with SSO logins or when provisioning to the downstream applications using this parameter.
If the application supports REST API, I would recommend switching to REST connector for this integration so that you can use a preprocessor and replace all the '#' in the username.