The free license restricts you to medium-density devices. For PolarFire, you cannot target the largest MPF500T devices (500K logic elements). You are generally limited to the PolarFire MPF300T and below.
Some advanced IP cores (e.g., PCIe Gen2/Gen3 root complexes, 10G Ethernet MACs, high-speed memory controllers with ECC) require a Gold license to unlock the RTL source or remove low-performance watermarks.
To be transparent, "free" does not mean "unlimited." Microchip reserves certain premium features for paid Gold licenses. If you rely on any of the following, you may need to upgrade: