Just an example if you have an audio interface with loopback ability.
This is without using Cubase’s Control Room so that it works in every version.
I create an output bus “To OBS” in Audio Connections. This gets connected to the stereo channel pair of my audio interface where I have activated loopback. In this example Adat 5 & 6.
If I only use 1 audio track I can use a Sends slot to send the signal to the “To OBS” bus. In OBS I will choose the pyhsical input from my audio interface where loopback is enabled. In this example Adat 5 & 6.
If you have several tracks you can route them all to a group track and use a Sends slot there.
If you have a version of Cubase that support “Direct Routing” you can use that instead of the Sends slot.