What is wrong with hydrolysed vegetable protein? It is a natural product of cooking vegetables.
You don't need stock to make good soups.
Finely chop a good selection of veg (onion, garlic, carrot, swede, leek, potato etc.). Put a little oil in a pan and coat the veg in it. When it starts to sizzle cover and turn the heat down low. The veg will sweat and release wonderful aromas. Stir now and then so that it doesn't brown.
After about 30 mins add the veg to whatever else you have cooked - lentils, split peas etc.
Alternatively boil up a ham hough and add everything to it.
I love making homemade soup/