Look for related markets adjacent to your core market.
Here’s a good example: Warby Parker sells eyewear online but they also have an app that allows any consumer with a phone to test eyesight.
The app doesn’t scream “buy our product” but is perfectly aligned with the problem Warby Parker solves.
Their eye test app is ranked #9 on Apple app store under the medical category. To get similar visibility on Google Warby Parker would have to spend millions. So it’s a genius move.
My only question is why didn’t a monopoly like Luxottica think of this first??