This article describes why some of the hardware model end-of-support dates cannot be found in the support portal: https://support.fortinet.com/Information/ProductLifeCycle.aspx
Scope
FortiGate.
Solution
Most of the hardware model end-of-support dates can be found in the support portal’s product life cycle:
But some of the latest model end-of-support dates are not published, for example, 400F or 401F as shown in the screenshot below:
Fortinet has not decided on the end-of-support date of these models yet. The user may check the support portal from time to time to get the EOS dates.