[pseudosaid]

A stereo mix is in fact trivial and roughly assumes a left right speaker arrangement. Software summing is math and is the same across digital audio workstations because math is math. Are there 3 or more microphones? doesnt matter, each mic is a mono input. trying to capture a facsimile of a perceived stereo field? use ORTF mic spacing and hard pan those mono inputs appropriately.

Stereo is just dual mono. its that simple. Summing is just math, its that trivial.

Creating a mix of multiple inputs for a stereo lr output? also completely trivial from a technical standpoint. Hardly trivial from a creative pov, but that isnt what this is about.