How to redirect sound sink to source
The automatic monitor that is created is not recognized by a lot of programs as a source. Try remapping the source:
pactl load-module module-remap-source master=alsa_output.pci-0000_00_1b.0.analog-stereo.monitor source_name=virt_mic source_properties=device.description=VirtualMic
That should show up in Discords list