Using USB out to record but monitor through other audio interface

Hey, using reaper on Mac. I can only set either the QC or my Scarlett 18i8 as an interface. I’d like to be able to record gtr USB from the QC but monitor through my Scarlett. I’ve got other hardware hooked up to my Scarlett and I’d like to send a pure digital signal from the qc instead of A/D/A/D conversion. Can’t find any workaround and I’ve been looking for 20 minutes haha