The LT3752/LT3752-1 is an Active Clamp Synchronous Forward Controller featuring internal housekeeping capabilities. It can regulate the output with or without an optocoupler. When using an optocoupler, a shunt regulator can be added to the design. This common approach is detailed in the document ds21-power_ your-isolated-system-effortlessly.pdf. The image below provides how the Shunt Regulator can be connected to the Optocoupler.
Another approach is by using LT8311, instead of using a Shunt Regulator, this controller provides control for synchronous rectification and Opto-Coupler driver for ease of design.