Regarding hardware solutions: Here are the settings for loop back if you use an RME interface.
- open TotalMix
- click on the wrench symbol on one of the Hardware Output Channels; I prefer to use an output for this that is not connected hardwarewise
- activate Loopback
In my example I use the channel SPDIF. So in Zoom or OBS I would set the audio input or microphone device to RME SPDIF. However, RME allows you to utilize any output channel for loopback.