Swabian lentil soup with spätzle

serves 4, I always downsize a bit, just taken straight from the website: https://www.tinastausendschoen.de/linsen-mit-spaetzle-rezept/

300g lentils (pardina? I dont know how these are called in english, but something a bit more rustic looking, not red lentils)
some form of mirepoix: classic french (onions, celery, carrot) or german Suppengrün (onion, half a celery root, half a leek stalk, carrot)
(less than 1 tablespoon?) tomato paste
bay leaf
butter
1tablespoon flour
some liters of broth, vegetable or beef
vinegar (eg balsamico, apple cider, ..)
salt, pepper
optionals:
for some more richness: a slab of pancetta or other bacon (pork belly might work?), in small cubes
potatos, cubed small enough so that they can fall apart after 30-45min of cooking. makes it more creamy/thick
vienna sausages - either warmed up separately in a pot with water, or sliced into rounds and added to the soup at the very end

steps:
ideally soak lentils for a few hours, eg overnight, but 3-6hours is enough too probably.
if you have bacon render out the fat and cook it for a bit in the pot you'll use to make the soup. remove just the bacon from the pot, leave fat.
add butter and melt, add flour and stir constantly to make a basic roux and cook off some of the raw flavor of the flour. add mirepoix, cook for a bit, add tomato paste and let the raw taste cook off a bit as well. add rest of the ingredients for the soup except vinegar and vienna sausage. add bacon back in, add broth, cook for 30-50minutes or so until lentils tender. if you added potatos you can smash them against the wall of the pot at the end of the cooking time.
serve with spätzle, vienna sausages, parsley or some other green stuff if you have