Yeah both serato and trakor from my experience are a bit like that in terms of “fuck you we are doing this” approach to their software.
I have just given it a quick 45 minute try (so not exhaustive) but unfortunately I don’t think it is where you want it right now. My motorised platters do not work with it that I can see and I cannot find any mention of stems, it isn’t something I use so I’m not that familiar with it.
The mapping on my controller seems to be pretty decent and the stems button I have does nothing so I’m guessing it isn’t a feature yet to have any kind of implementation :(