Yes, you need to use the Sbus serial port as I indicated above. That is a function of the receiver, not the transmitter. The R88 can do Futaba or FrSky, doesn't matter which you use, but you must use the Sbus serial port connected to the Aura5.
You will need to assign a switch on the transmitter to Output on channel 5. The Aura defaults to the flight mode being on channel 5