Turn on a multi-functional pressure cooker (such as Instant Pot(R)) and select Saute function. Add turkey and seasoned salt; saute until browned, about 5 minutes. Remove turkey.
Melt butter in the pot. Add carrots, celery, and onion; cook until just starting to soften, about 5 minutes. Add flour, dill, and pepper; cook for about 1 minute. Return turkey to the pot; add broth and potatoes. Top with cauliflower. Close and lock the lid.
Select high pressure according to manufacturer's instructions; set timer for 10 minutes. Allow 10 to 15 minutes for pressure to build.
Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove the lid.
Remove the cauliflower and 1 cup of the soup liquid; blend together until smooth and creamy. Add Cheddar cheese and season to tate. Stir cauliflower puree into the pot with the rest of the soup until cheese is completely melted.
