Store autocomplete is the cheapest keyword research there is. Those suggestions are ordered by what people really search, and both stores hand them over for free.
The Autocomplete Simulator queries them for you. Type a prefix, pick a country and a language, and the live suggestion lists from the App Store and Google Play come back side by side. Run it on your brand, your category, a competitor's name, or the two letters your app name starts with.
Every run is saved, and that is where the value compounds: a suggestion that appears, climbs, or disappears from a prefix is a demand signal that arrives weeks before it shows up in anyone's rankings.
The simulator is in the Tools section of the dashboard.