The uTrack24 has 3 different modes.
USB host player (the inputs are muted)
USB host recorder (the outputs are muted)
USB interface mode (you need to connect to a computer)
In USB interface mode:
In the uTrack24 you need to select between to use analog or digital inputs (in 3×8 channels groups)
The outputs are using the analog and the digital in the same time.
Please take a look at the signal flow: