I’m not a vegetarian but still have lots of fiber and vegetarian protein in my diet.
fiber sources:
soluble fiber - boiled tapioca, sabudana, raw banana (plantain) dishes with as less oil and spices as possible, pulses (white/brown channa, field beans etc, avoid kidney beans due to high lectin content), inulin supplement.
insoluble fiber - salted makhana, boiled moong dal/horse gram sprouts, usual veg side dishes, stir fried/sauteed vegetables (broccoli, red cabbage, bell peppers, zucchini, carrot, beans etc), raw coconut chunks, amaranth greens, moringa greens, berries, low sugar fruits, pineapple, seeds (flax, pumpkin, watermelon, sunflower, avoid chia seeds due to high lectin content), psyllium husk with plenty of water, (avoid spinach due to high oxalate content).
vegetarian protein sources:
tempeh, boiled horse gram sprouts, A2 butter, well boiled peanuts, pistachios, millets (also for fiber, better as fermented), pulses (see above), legumes (keep chana dal to minimum due to high lectin levels), mushrooms.
better to take digestive enzymes supplement and herbs like saunf, pudina leaves, dry ginger etc. if still low digestion then betaine HCL also can be taken under doctor supervision till natural stomach acid levels improve.
vegetarian fat sources:
A2 ghee, cold pressed cooking oils (coconut, sesame), nuts (walnuts, macadamia, hazel, brazil nut, pecans), seeds (see above)
In addition to the above macros, include fermented foods as frequently as possible. if there is no histamine reactions. then proceed slowly.
Beware that you have to gradually increase you fiber intake over several months. Sudden increase will cause boating, pain and gut discomfort. But if such symptoms persist even after a few weeks then gut needs to be checked for any infection or overgrowth issues life SIBO/SIFO etc. in those cases proper treatment along with low-FODMAP diets etc need to be followed till it gets normal.