Hi Ronin1973,
The Doepfer A-138m Matrix mixer can be used in stereo operation too. Just use for example inputs 1 & 3 as your left inputs and inputs 2 & 4 as your right channel inputs. Then with the 16 knobs you can do panning. You can create either two times a stereo output, or what I usually do, just one stereo output, meaning output channel 1 is my left channel out and output channel 2 is my right channel out, those two outputs then to any Audio Interface module to output it to an external mixer. Seems to work quite well.
Or you can use it as 4 mono inputs and one stereo output (or two stereo outputs) or you could even do one stereo input (for example input channels 1 & 2) and two mono inputs (channels 3 & 4 in this example) and again one (or two) stereo output(s).
So... I don't see the non-stereo issue, for me this is stereo enough :-) One even could extend it to a quad output (instead of one or two stereo outputs) :-) Kind regards, Garfield.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads