People are too worried about rogue Chinese stuff - the e-bike stuff is pretty organised. One common issue is PAS sensor compatibility, as different manufacturers can't decide on male/female plugs...
This is the KT-3 you're on about, it works with most modern Chinese controllers (mine is by Risunmotor). I got this off ebay. The plug it uses is generic, white with five wires in a straight row. Seems like all the current Chinese controllers of 36v/48v have a plug for it, as other LCD displays also use the same plug.
I really like it. It has a few quirks, but can be quite well customised via a long list of parameter settings - tutorials on YouTube educated me on these.
