Placing UFL connector in 3G dongle
It appears that the two parallel strips of solder are for mounting the shield to a connector and there is a small component in series with the signal passing to the left into the small red brick. My answer is conjecture and comes without warranty of functionality as it requires removing at least one component from your device.


Red: what looks like the current antenna.

Dark blue: approximate position of connector.

Light blue: SMD component that would be in the way of the connector's center pin.

Additionally, note that your device has solder pads for metal shields over its RF components on each side, but those shields were not placed during manufacturing.