Edit:
ok, seems to be an “issue” with the fact that i sit on a new M1 macmini.
and also is it looking that the new mac is something different on the aspect how easy it is for external apps like “blackhole” or “loopback” to get access to their audio access points, under the hood.
Loopback (rogue amoeba) has a Beta out,
but the installation of the underlaying ACE app requires some “juggling and adjustments” in the security dialog of the system settings.
so, there´s a change here with the M1 macs it seems
i just tryed to work with two instances but i failed. ( macOS Big sur )
i use Blackhole 16CH.
The signal would go out at the first Gp3 instance, but not coming in in the next GP3.
the audio settings are accordingly in both GPs instances.
i created a aggregate file,
but it seems to me the failore is there.
(on audio midi setup) it shows in the left: 0 inputs, 2 outputs.
also if a try to adjust Blackhole allone ( non aggregate) i allways just get a master fader that i can set to on. the other faders are greyed out/inacessible.
what can i try ? macOS big sur ( a totally fresh installation, in fact a new mac (mini) )
Blackhole was rated as Big sur compatible