Turn on a multi-functional pressure cooker (such as Instant Pot) and select Saute function. Melt butter and add onion, carrots, and celery. Saute for 2 minutes. Sprinkle flour over the vegetables, stir, and hit cancel.
Add broth, chicken, lentils, parsley, paprika, dill, and thyme. Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 8 minutes. Allow 10 minutes for pressure to build.
Release pressure using the quick release method according to manufacturer's instructions, about 5 minutes. Turn the pot off and remove the lid. Stir in noodles and lemon juice. Let sit for 15 minutes or until noodles are cooked. Ladle into bowls and salt and pepper to taste.