You're going to need a master section to go with the Tex Mix stereo module - https://www.modulargrid.net/e/tesseract-modular-tex-mix-master-section

Befaco's ST Mix gives 4 stereo channels in a smaller space but doesn't have send & returns, mutes etc., and depending on where you're audio goes after it you might need an output model e.g. ALM HPO (you could of course be going straight to an outboard mixer)