Is there a way to determine which antenna connector is for which radio on a cellphone?
Those connectors are for GPS, WiFi, Bluetooth, Cellular -- none of them are connected to the FM radio input pad on the radio chip. If you don't want to plug in a headphone, you could use this antenna which is designed to plug into the headphone jack. Or solder a wire into a headphone plug (use the shell contact) and you're there. If there's no room to insert a headphone plug, just solder a 75 cm (or 2 ft) long wire to the shell contact of the headphone socket on the PCB.