well given how easy it is in china to get a mainboard made for you - it's not unreasonable to think that tronxy have done just that and wreitten their own firmware.

machine's new to me I'll go look at one :-)

Okay so it's 500 sa with a 2-in-1 out extruder setup.

Honestly, unless it's done right (and while I know the right way to do it, I've never seen a mix nozzle that does it properly) a dual mix nozzle is probably the worst way to iimplement dual extrusion.

The reason being that how do you clean the nozzle chamber out between changing filaments ?
It also means that you can't mix filaments with different extrusion temperatures.
And unless there is an actual mechanical valve that shuts off the filament not being used, there's no way to avoid bleeding between the two colours.

BUT (lol) it's a pretty common setup, so as long as your firmware supports both core-xy and dual mixing nozzle - absolutely no reason you need to stick to the tronxy firmware.

Also interested to know how effective tronxy's 2-1 setup is.

Please keep us posted on your progress - I'm more than willing to be proved wrong on this setup :-)