One option is to wait for v1.5, which apparently has DCAs for the whole Qu range.
As the Qu16 doesn’t have dedicated subgroups, Plan B is to use your mixes as subgroups, and return them to the stereo inputs.
Un-assign ch 1-16 from LR.
Assign your vox channels to a stereo mix (eg mix5-6) post fader at unity, effectively using the mix as a subgroup.
Assign your drums to another stereo bus (eg mix7-8.)
Run cables out of the physical XLR outputs of these mixes into the TRS sockets of two of your stereo inputs (eg mix5-6 to st1, mix7-8 to st2.)
St1 is now your vox master, St2 is now your instruments master. Ensure St1 and St2 are assigned to LR.
As long as you’ve got channel faders up, the mix5-8 masters up, the St1+St2 faders up and the LR fader up you should hear sound.
Be aware of your panning: you have to do it in the mix rather than the LR pan.
Be aware of where your fx returns are routed and whether raising St1/St2 will affect the dry sound or both dry and wet sound.
HTH
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