If you don't want to see non-installed Setapp apps in your Spotlight search results, disable this feature in Setapp Preferences:
- Click the Setapp icon in the menu bar (upper-right corner).
- Click the gear icon and choose Preferences.
Alternatively, open Setapp and choose Setapp > Preferences.
- Deselect the checkbox next to "Spotlight search."
On macOS 12 (Monterey), this feature is disabled by default.