Defining the 3D LUT folder does not define any style.
Exactly which Fujifilm simulation are you trying to use? There are a few, some being simply LUTs that you can apply, some being complete styles with multiple elements, some even use Lua scripts (see GitHub - bastibe/Fujifilm-Auto-Settings-for-Darktable: Automatically apply Fujifilm film simulation LUTs, crop, and DR correction when importing images in Darktable, for example).
There’s an extensive thread here: Replicating Fujifilm JPG colors from raw files?