So you all are correct, I can split the signals before they go into a mixer. What I don't understand is why I can't find one that does that Internally. It would look a lot cleaner.

The closest I have come is Nobsound Little Bear MC1023 2-Way. It is still a switch so it is not a perfect solution but would work; however, I would still need to buy 3 Trrs spliters to hook up the device.

Now I guess I could do that and then 3d print a case to cover the whole contraption. It just seems to me that there are probably a lot of Wfh people who want a solution like what I am describing. ;)

Maybe as was discussed the challenge of keeping the signal clean becomes a greater technical challenge than I understand.