This instructions can be technical, so I ask of you to please have patience and persevere. Have a developer mindset and debug when encountering issues.
The idea is that you will use Loopback to capture audio as a Mic source for Vesktop to pick up and use for screensharing. At the time of writing, Vesktop does not support soundsharing for MacOS. So we will fix that. An issue has been filed for Vesktop to build support for MacOS soundsharing. Vencord/Vesktop#472