Don’t worry about what’s LAB and what’s not. LAB is not bad, neither is it evil. Under certain conditions, it works well. The darktable developers have done their best to put modules where they usually work best, but you can rearrange them. If a given module does not work (pushed too far, or it just can’t do what you tried to use it for), you’ll see it clearly. In that case, adjust it or try another. Read the filmic FAQ (darktable's filmic FAQ). A quote:
(from @aurelienpierre ) What if I like to use the display-referred Lab tools ?
Remember filmic is your conversion from scene pipeline to display pipeline. All the Lab modules can still be used in conjunction with filmic, even though they are not optimal.
Sharpening, contrast equalizer, high-pass and low-pass filters work in Lab but perform local operations, so they don’t rely on any definition of grey or white. As such, they should go before filmic (where they are by default in the 3.0 pipe order).
Levels, tone curve, zone system, etc. have a display-referred GUI (in the 0-100% range). These modules rely on a fixed assumption about the values of grey and white. These should better go after filmic, where the pipe is dislay-referred.
Local contrast is a local operation that rely on an hard-set definition of grey and white. For some reason, I sometimes find it works better before filmic, and sometimes really not, while it always works ok after filmic (where it is by default in the 3.0 pipe).
Check out @s7habo’s youtube channel https://www.youtube.com/playlist?list=PLmZmCIhOC2Frt6Wq3gc0-egOy_P1sXjau and take his advice:
Just to reassure you: Since you don’t mix dangerous chemicals, but only harmless modules, you don’t have to worry that when you make a mistake, the whole neighborhood needs to be evacuated.
And B&W Processing with darktable - module choice & ordering
The modular structure of darktable is the ideal playground for this. I wish people wouldn’t be so scared and dare to experiment with modules much more.