Bile salts are important in regaining the ability to digest fat. Also, high stomach acid triggers the gall bladder to increase the strength of the bile salts so I use apple cider vinegar daily. I’m 45 and stomach acid generally weakens with age so that helped me out.
I’m an advocate of pre and probiotics to reset the gut. For me, the fiber (pre) is not really necessary unless you eat a lot of veggies and need the fiber to ferment into short chain fats. It actually slows down the process of elimination. I used to need fiber but since I’m mostly carni with some exceptions, it’s not a big factor.
My go to is fermented veggies and cheeses- pickles, sauerkraut, kimchi, blue cheese… that’s the good stuff