So in the end, darktable is open source, and the code is there for all to see.
What I see when I look at the code is that there is no application of base curve or filmic. The code will create an instance of the “tone curve” module if you have made adjustments in Lightroom. I still have a couple of xmp files from Lightroom, but there the tone curve definition is linear, and so darktable doesn’t bother to create any tone curve instance.
So, you probably know that if you look at a flat raw file with no tone curve at all, it will look dark and low contrast. Therefore, it seems clear to me that the intention was for the base-curve to be applied, and then other modules from the lightroom XMP applied on top (like crop and rotate, vignetting, etc.). However, if you use the scene-referred workflow, then the basecurve is substituted with the filmic rgb + exposure modules, and this is equally fine if you set up an exposure auto-preset suitable for your camera. It just comes down to which workflow you prefer to use.
The only area of doubt I have is about this tone curve that could be created. I don’t have any lightroom XMPs which contain this, and I no longer have a copy of lightroom with which to make a test edit. The concern is whether the tone curve coming from lightroom is relative to lightroom’s “base curve equivalent”, or whether it is relative to the original raw. If the latter is the case, and you have base curve or filmic rgb also active, then you will end up with an overly bright overly contrasted image.
I would “guess” that it is actually the former case rather than the latter, but perhaps if you still have lightroom, you can make a test (make some tone curve modification in lightroom, import the image into darktable, and see whether the darktable tone curve module is complementing or is “doubling up” with the base curve). Then you can let us all know if my guess is correct
[edit: in both display-referred and scene-referred, the module order still places tone curve AFTER base curve or filmic, so the different module ordering between the two workflows doesn’t matter in this case)