You should set the MIDI setting to 16 bit 44.1 Khz not 48 Khz and then download and install the Bitperfect program from here: https://apps.apple.com/se/app/bitperfect/id455545700?mt=12 and let the software lock to the clock frequency in the MAC, then the Bitperfect program will communicate with the U-Clock.
You get this pops and clicks because of the DAC and U-Clock does not get the correct word.clock signal.