Yes.
Stand-alone operation
With a standard USB-C power adapter, the M4 can be used as a stand-alone preamp and basic mixer, with no host computer required. Simply engage the monitor button for all four inputs (and 48V phantom power, if needed) and adjust the preamp gain as needed. Connect the main outs to any line level destination, such as a PA or patch bay.
That’s from the Motu website but I confirm that it works.