UFSM is automatically applied in the background to all students that are enrolled in a Reception, Year 1 or Year 2 year group curriculum grade. You can see further details here: Set a student as Universal Free School Meals (UFSM)
This means there isn't an out of the box demographic specifically for Universal Free School Meals (UFSM).
Instead, use the report here: See a list of FSM Free School Meal students
Filter your results to only look at students in Reception, Year 1 or Year 2.