Qtractor DOES work with sidechain
Tutorial and Examples Proyects:
https://sourceforge.net/p/qtractor/wiki/How%20To%20-%20Sidechain%20Work…
----
It's as simple as creating a bus with extras chanels.
These extra channels are occupied by the sidechain.
Then with inserts we route the signal to the sidechain.
We all thought it wasn't possible, but since version 9.35 inserts work more reliably... there is no problem creating these types of flows.