When adding a new operator to your Uptrends account you can choose between a manual setup or sending an invitation and letting the operator choose the login credentials.
From now on, inviting operators that use SSO is also supported. Note that you have to enable both the username/password and the SSO login options for the new operator. The setting is on the Main tab of the operator (individual) or the account default settings (account-wide). If only the SSO login option is enabled, you cannot send an invitation.