While working with chat.openai.com we worked out that SSO=true would be the right option. However this does not work. openai informed me that FortiClient VPN is not supported for iOS by Fortinet. So we would need Fortinet to add this functionality if we want it to work. Right now I am using the QR code but then having users go back in manually to enable the SSO option.
The Fortinet Security Fabric brings together the concepts of convergence and consolidation to provide comprehensive cybersecurity protection for all users, devices, and applications and across all network edges.