Ubiquiti mesh usb mod

Hi,

i want to know if i can add an usb port to the unifi mesh device i use this device with openwrt and travelmate on my caravan. but on some campings there is poor wifi and want to use LTE / 4G with an dongle.

https://openwrt.org/toh/ubiquiti/unifiac

hope someone can help me with this.

Arco