Gregory's Server
this system uses two extruders: one direct drive (stock) and one bowden (bolted to the side). this is apparently important for something
doesn't blob on tool change, doesn't jam too often, uses a complicated system of gcode macros to track the state of material multiplexing unit so that the slicer can issue a single command and have it ready (other than purging), requires only a few screws and a pneumatic fitting to assemble
check out this lighthouse she made!!!
(for some reason PrusaSlicer divides by zero if she tries to make a normal multi-material object, and a lighthouse was the obvious candidate for manually inserting material switches between layers)