The Soundly Monitor VST3 and AAX plugins serve as a virtual audio output from the Soundly App to your DAWs.
Soundly Monitor is prefered over ReWire as it offers full multi-channel support.
To change the number of output channels in the plugin, you must first disconnect by selecting another output device in Settings and then reconnect to the plugin.
The plugins comes pre-installed on Windows. On Mac, go to Settings and install the plugins under Audio Device